follow up issue #98 - improved git-cmd.bat

I propose this improvement to your git-cmd.bat file. Because you have no "develop" branch, I send you this pull request against your master.

* Tested for the portable git version on several Windows XP SP3 systems.

Added comments and settings for

- proxy (optional)
- drive and path for the started shell
- when started, "git --version" is automatically run
- verbosity level of curl (optional)
- Window title is now "Portable git shell"

Sources (Urls) are included as comments.