Generate standard configuration meta-data

Update the `spring-boot`, `spring-boot-autoconfigure` and
`spring-boot-actuator` project to generate configuration meta-data
files during compilation.

See gh-1001

spring-boot-actuator/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -0,0 +1,8 @@
+{"properties": [
+  {
+    "name": "spring.git.properties",
+    "dataType": "java.lang.String",
+    "description": "Resource reference to a generated git info properties file."
+  }
+]}
+