Rework of show-server-revision

Changes Show-Server-Revision to be a text output containing a link to server's commit that opens in user's default browser.

Adds Github and Report Issue button to UI interface.

Removes git_host.txt and adds github url to config.txt

Adds link to issue format on wiki to contributing.md so it shows up in link given when making new issue.

New show-server-revision
![textput](https://cloud.githubusercontent.com/assets/4343468/3658286/a24dd31c-11a1-11e4-8578-bac31b8bfc94.PNG)

New buttons
![buttons](https://cloud.githubusercontent.com/assets/4343468/3658288/a8c20eac-11a1-11e4-9c36-b3031d44d33a.PNG)

changelogb?