Support repository-specific configuration files

This is the first time I've used Git, Git-hub and of course pull-request.

My commits include my version of the Vault DLLs (5.0.3). If you do mine first and then apply the other pull-request then later ones will be applied - 6.0.1.

I started off with command line overrides for settings which are repository specific. Then I found a way to get a .config file from any directory and so now the default is to get it from the current directory - presuming Vault2Git.exe is in the path and the current directory is the root of the git repo.