Added some CRAZY hawtness to envsetup.sh

-bash completion for git command and remote+branch names
-branch of git repository in which working directory is rooted displayed on PS1
-added rst and rup helper scripts (rst <branch name> is repo start <branch name> <projects>, where projects is the project containing your working directory, unless otherwise specified

Change-Id: Ie9249998ff43ddebaa1d29128e0e5061759740a0