Detect HEAD and place it accordingly with special color

* on the branch ref if the branch is checkouted
* on the commit if detached head
Display different style for types of references

Note: we can't be sure that a ref is a remote,
so looking for ref containing "/" which should
be sufficient for a demo repository...
Add open folder button
Accept a repository path as a command line parameter

Let GitViz be added to the "Send to" contextual menu
%APPDATA%\Microsoft\Windows\SendTo
Auto resize windows to better display the DAG