Extract config server properties to Java bean

ConfigServerProperties is now used to store global properties
for the config server (like the path prefix and bootstrap flag)
under spring.cloud.config.server.* so git specific ones have
been pushed down to spring.cloud.config.server.git.* (similarly
for git->native).

At the same time introduce spring.cloud.config.server.defaultLabel
for the deafult git label (defaults to "master").

Fixes gh-28

spring-cloud-config-server/src/test/java/org/springframework/cloud/config/server/ApplicationTests.java

@@ -18,7 +18,7 @@ import org.springframework.test.context.web.WebAppConfiguration;
 
 @RunWith(SpringJUnit4ClassRunner.class)
 @SpringApplicationConfiguration(classes = ConfigServerApplication.class)
-@IntegrationTest({"server.port:0", "spring.config.name:configserver", "spring.cloud.config.server.uri:file:./target/test-classes/config-repo"})
+@IntegrationTest({"server.port:0", "spring.config.name:configserver", "spring.cloud.config.server.git.uri:file:./target/test-classes/config-repo"})
 @WebAppConfiguration
 @ActiveProfiles("test")
 public class ApplicationTests {

spring-cloud-config-server/src/test/resources/configserver-test.yml

@@ -2,4 +2,5 @@ spring:
   cloud:
     config:
       server:
-        basedir: target/config
+        git:
+          basedir: target/config