Make spring-boot-config-metadata/pom.xml work 'out of the box'.

Small changes I needed to make to get the sample to compile properly after importing into Eclipse.
  
   - change from SNAPSHOT to 1.2.0.RC2 dependencies 
   - add milestone repository to resolve 1.2.0.RC2
   - specify java compiler level (seems like 1.6 is the minimum to avoid interface @Override warnings)