Completely reorganised git aliases

Reorganized aliases in the git plugin.

This reorganizes completely the way each alias is defined in the Git plugin. They now follow a common logic:
    
- they are organized in group with the same prefix, some may overlap (like gc for git commit and gco for git check-out) but there is no more collision (gp for git push and gpr for git pull --rebase)
- they are much easier to learn since they are no more in a single list
- more documented!
- they are logicaly liked to each other, they do not hide the underlying git command so you can easily remember them when you have to work on a machine without these magic aliases.
- I use them daily in my git workflow (pull/rebase, dev, rebase, push, ...) on both my android tasks and github projects.

Signed-off-by: Gaetan Semet gaetan@xeberon.net