Added ItemDiscover, ItemCancel, and ScmTag permissions to the enum

These additional permissions should be useful for other standard permissions.
Reorder enums to reflect ordering in the Jenkins GUI

This is more of a readability enhancement which could potentially be useful in the event that other permissions are added to Jenkins in the future.
added more support for the git plugin
added some default parameters
reproduce the defaults of the Git Plugin 2.0 while keeping compatibility
Merge pull request #108 from jenkinsci/git-closure

added more support for the git plugin
Merge pull request #97 from justinharringa/patch-1

Added ItemDiscover, ItemCancel, and ScmTag permissions to the Permissions enum
Releasing 1.20
Bumping to next rev
Merge remote-tracking branch 'upstream/master'