Update `LogbackLoggingSystem` to call the `reset()` method on the
`LoggerContext` before initialization.

This will hopefully reset the context to prevent the same appenders
from being accidentally added more than once.

Fixes gh-1091

This is a continuation of the changes made in 611f9781. It makes some
more @Bean methods public and adds tests to spring-boot-actuator and
spring-boot-autoconfigure to prevent against non-public methods being
introduced in the future

Closes gh-1571

Cherry pick documentation updates which appear to have been
lost during a previous merge.

Fixes gh-1523
Cheery-picked from 16c2477d

Fixes gh-1571

Conflicts:
	spring-boot-samples/spring-boot-sample-tomcat-ssl/pom.xml
	spring-boot-samples/spring-boot-sample-tomcat-ssl/src/test/java/sample/tomcat/SampleTomcatSslApplicationTests.java
	spring-boot/src/main/java/org/springframework/boot/context/embedded/ConfigurableEmbeddedServletContainer.java
	spring-boot/src/main/java/org/springframework/boot/context/embedded/Ssl.java

Fixes gh-1570
Cherry-picked from 0960908b and 258c6f11

Fixes gh-1548 again

Previously, EnableAutoConfigurationImportSelector assumed that it
would always find auto-configuration attributes from an
@EnableAutoConfiguration annotation. This assumption does not hold
true in certain circumstances, although exactly what those
circumstances are is unclear. It could occur if the import selector
were used directly, but it's package-private making that unlikey. In
such circumstances a NullPointerException was being thrown.

This commit asserts that the attributes are non-null and, should the
assertion fail, produces an error that is more helpful than an NPE.

Closes gh-1512

Closes gh-1522

Enhance JacksonAutoConfiguration to configure features on the
ObjectMapper it creates based on the following configuration
properties:

spring.jackson.deserialization.* = true|false
spring.jackson.generator.* = true|false
spring.jackson.mapper.* = true|false
spring.jackson.parser.* = true|false
spring.jackson.serialization.* = true|false

The final part of each property name maps onto an enum. The enums are:

deserialization: com.fasterxml.jackson.databind.DeserializationFeature
generator: com.fasterxml.jackson.core.JsonGenerator.Feature
mapper: com.fasterxml.jackson.databind.MapperFeature
parser: com.fasterxml.jackson.core.JsonParser.Feature
serialization: com.fasterxml.jackson.databind.SerializationFeature

Closes gh-1227

Update PoolingDataSourceBean.getParentLogger() to directly call the
method rather than use reflection. Also removed the logic from
`DirectXADataSource` since any fix there should really be applied in
the DataSource being wrapped (and not the wrapper).

See gh-1518

Conflicts:
	spring-boot-docs/src/main/asciidoc/howto.adoc

The repository configuration is there in 1.1.x but missing in master.
This commit brings the two branches back into line.

Closes gh-1473

Closes gh-1540

The fix for gh-1475 introduced the use of an artifact's group to
discriminate between two libraries with the same name (artifact id)
and version. However, in the case of Gradle, a group name was not
provided for libraries that have been resolved from a repository.

This commit updates ResolvedArtifactLibrary to use the group obtained
from the underlying ResolvedArtifact as its discriminator.

Fixes gh-1543

Previously, JTA auto-configuration would fail with a variety of
ClassNotFoundExceptions and NoClassDefFoundErrors if it was used with
an “incomplete” classpath. This commit adds a number of classes to
@ConditionalOnClass annotations so that the auto-configuration backs
off gracefully in the absence of certain classes.

Specifically, the following now work as expected:

 - Deploying an app to a server with JTA available via JNDI when the
   app does not use transactions
 - Auto-configuration of Atomikos without JMS
 - Auto-configuration of Bitronix without JMS

Both XADataSourceAutoConfiguration and JndiDataSourceAutoConfiguration
have been updated to back off in the absence of spring-jdbc; a
dependency of DataSourceProperties which is used by both classes.

Error handling in AtomikosDependsOnBeanFactoryPostProcessor and
BitronixDependentBeanFactoryPostProcessor has been enhanced so that the
correct dependencies are established, even in the absence of JMS.

Fixes gh-1538

User can set those properties (optionally) to use a different
DataSource than the default.

Fixes gh-1558

With this change I got a simple Eclipselink version of the data-jpa
sample working. I'll push that when I get time to research it a bit more
(I needed to set up a Java agent so either that might be a problem
for our integration tests if we can't work around it).

Fixes gh-1268. Cherry picked onto master after (apparently) a failed
merge of commit ac2ab39a.

When MVC path matchers are used as metric keys, they can still contain
invalid characters and patterns (like asterisks). This change removes
some more special characters and also tidies up the names a bit so
no key part starts or ends with "-" (which is ugly).

Fixes gh-1528