tweaks: Migrate OS tweaks to the tweaks package

This removes much of the OS customization code from the makefiles and
stuffs it into a package instead.

This also deprecates and removes the aiy-board-resizefs package in
deference to the aiy-board-tweaks package (which really should probably
be renamed).

Change-Id: I459ec070b248594ef52f5d26cd9c7090300c6c0e
2 files changed