cherries.sh: Add capability to cherry-pick non-gerrit commits

Adds code to cherries.sh to allow properly formatted patches for any commit
from any code repository, local or online to any source folder in the build.

Online code by Lukasz

Change-Id: Ie612e026260e5c5d820c8372b864670cc5af6633
Merge "cherries.sh: Add capability to cherry-pick non-gerrit commits" into pac-4.4