New aliases for repo plugin

This helps a lot in day to day android development:
- rs: repo sync (git fetch on all projects)
- rra: auto rebase for all projet without loosing uncommited changes
- rsrra: do both steps at once

Signed-off-by: Gaetan Semet <gaetan@xeberon.net>
Merge pull request #2086 from Stibbons/gsemet_push_repo

New aliases for repo plugin