Correct executable bit for source files

Many media files and source code files were marked as executable in Git.
Remove those.

Also a shell script and python script were not marked as executable.

Change-Id: I59423c5d04b04e0665e8e3c77174fcbef26b3db0
Signed-off-by: Chirayu Desai <cdesai@cyanogenmod.org>