ls-remote to lookup references in a remote repository

List references, like heads or tags, in a remote repository
without depending on a locally cloned workspace.

The git-parameter plugin lists branches or tags on a local
cloned workspace, so it doesn't work on the first build or
if user wipes out workspace.

If user only wants a tag name with its commit id, there is
no need to clone the whole repository.
Merge pull request #150 from yestin/master

ls-remote to lookup references in a remote repository
Merge branch 'jgit-references' of https://github.com/pauxus/git-client-plugin into master-pauxus-jgit-references
Enable test_branchContainingRemote - broken by changes, needs work

Also removed the ugly adaptCliGitClone method, replacing it with the
more direct, and more clear "git.checkout()" call.
Merge pull request #1 from MarkEWaite/master-pauxus-jgit-references

Test simplification and more