[cleanup] cleanup pom before next release

* adjusted pom to maven code convention: http://maven.apache.org/developers/conventions/code.html
* introduced updated profile 'release', to release the scim-schema to maven central, without the load of the sonatype parent pom
* updated integration profile to snapshot profile
* updated developer to the OSIAM team dev
* changed release tag from scim-schema-{version} to v{version}, like the other OSIAM projects
so it can be removed there, too, next time we change the pom (i.e. before the next release).