Add the repository-specific git config include (git >= 1.7.10)

Add the repository-specific git config include (git >= 1.7.10)

!!! NOTE - potential security RISK !!!

 You *MUST*
  - check the file is legit:
     git diff 7eb1f0e165a4 maint/git_config_dbic.inc

  - copy the file to your .git directory:
     cp maint/git_config_dbic.inc .git/

  - and include it:
     git config --add include.path git_config_dbic.inc

 **NEVER** include the file directly from the repository itself, e.g.

 [include]
   path = ../maint/git_config_dbic.inc

!!! NOTE - potential security RISK !!!

Adds extra maint-specific repositories, and defines two gitk shortcuts:

 `git vis` - showing all current heads/stashes of interest in progress
 `git prvis` - showing all unattended to github PRs