Gradle build for PCGen
- Add svn commit and tag support
- Add prepareRelease and pcgenRelease tasks to achieve the major steps in releasing.
- Add descriptions for all release tasks.
Issue#: CODE-2597


git-svn-id: svn+ssh://svn.code.sf.net/p/pcgen/code/Trunk@24434 ef53c05b-3124-4d59-ae7d-fe3273f42be7