Use org.springframework.boot instead of ${project.groupId}
groupId in order to make it easier to use spring-boot-samples
modules as a starting point for new projects.

Fixes gh-447

This turns out to affect JPA, but only because it looks for a URL for the
root of the classpath using ClassLoader.getResource("") which barfs in
an app launched from an executable JAR. It's easy to make a special case
for "" in the class loader, so I went ahead and did that. Possibly need
to think what the implication of getResources("") is as well (not
tested in an app yet).

Fixes gh-420

Fixes gh-441

Profiles set with Environment.setActiveProfiles() (rather than
spring.profiles.active) *before* any config files are processed, are
treated as "additional" (to the ones supplied in spring.profiles.active
from all sources, files and System properties included).

Fixes gh-429

Fixes gh-438

Fixes gh-417

RC4 added a ServletRegistrationBaen for teh DispatcherServlet and we
didn't register a MultipartConfigElement if one was present.

Fixes gh-427

Fixes gh-424

Fixed gh-428

Fixes gh-430

Fixes gh-433

... leaving only the embedded Tomcat enabling feature (registering
the WsSci).

Fixes part of gh-65

* patch-2:
  Correct link to samples.

Fixes gh-415

Rename ErrorWrapperEmbeddedServletContainerFactory to ErrorPageFilter
and extend AbstractConfigurableEmbeddedServletContainer rather
than AbstractEmbeddedServletContainerFactory.

Fixes gh-416

Rename ConfigurableEmbeddedServletContainerFactory to
ConfigurableEmbeddedServletContainer and extract
AbstractConfigurableEmbeddedServletContainer from
AbstractEmbeddedServletContainerFactory.

Update ConfigurableEmbeddedServletContainerFactory to no longer directly
extend EmbeddedServletContainerFactory.

Remove getPort() from ConfigurableEmbeddedServletContainerFactory to
keep the interface primarily setters.

There's no explicit support for older Servlet specs in Spring Boot,
but we can at least make it easy for others to provide such
support by not adding stuff to the context when in an older container.

Useful sample for common use case where user adds custom Authentication,
a form login, *and* global method security all the the same application.

Some assumptions were being made in tests, e.g. about
there being an AuthenticationManager @Bean, which were
false with the new Security 3.2.1 updates from Rob.

Also parent-child contexts with the actuator were
problematic because they didn't exclude the web configuration
for the management security in the parent context.

Fixes gh-244

Also change strategy for defaulting of Authentication. Spring
Boot authentication defaults are now encapsulated and can easily
be overridden by a user defined AuthenticationManager.

Error pages are a feature of the servlet spec but there is no Java API for
registering them in the spec. This filter works around that by accepting error page
registrations from Spring Boot's EmbeddedServletContainerCustomizer (any beans
of that type in the context will be applied to this container).

In addition the ErrorController interface was enhanced to provide callers
the option to suppress logging.

Fixes gh-410

Fixes gh-411