Created a DSC Resource for keeping Git repository in sync

Written this to keep a local git repository in sync with a remote repository. Planning to use for dev/test environment. 
Where are `$url` and `$file` coming from here ? They're not parameters to InstallChoco, and I don't see them set in a parent scope.

Also, along the same lines as pulling InstallGit functionality out of cGitPull, it's probably better to have a resource that installs Chocolatey itself be separate from the one that is responsible for using Chocolatey to install other packages.  Anytime a resource is installing its own dependencies, that's a pretty good red flag that you should really have at least two resources that are chained together with `DependsOn`