Update merge script to merge 7.0 to 7.1

* Refactor so that source and target branches are defined in
variables in the beginning of the script.
* Pass a dummy commit message to the merge to avoid opening an editor
while running the script

Merge: manual

Change-Id: I76c001b3bfcfd2dbb1ce2e9ec1b730641df31a77
Update merge specification for the master branch.

Change-Id: Ia8ad2d2e44e2d29bfa9e2271e4e4cad0a672ec22