setup.py: Make the modules selectable for install
setup.py: Map the USE flag keys to the module names
Moves archive.py to overlays

{squashfs, tar}.py: reflects moving of archive.py in dependencies.
config.py: Blanks out squashfs_command

Due to squashfs not needing to run a command aside from mount and
umount (which are handled by the Mounter() class), the config
option was set to a blank value.

layman.cfg: Reflects change to squashfs_command option with
explanation to user.

config.py: Also removes clean_tar from the true false check in favor
of the clean_archive config option.
squashfs.py: forces is_supported() to return True
svn.py: decodes stdout output if applicable

Fixes commit: f1db156a7d11e0bfb8d7b6a19f066c5d0b0fba5d
Thanks to Arfrever for his assistance in optimizing the code.
api.py: Fixes lack of syncing overlays
api.py: Fix an indent error preventing syncing

This correctly fixes commit: 964bb33df4a75
Subject: api.py: Fixes lack of syncing overlays
Author: Devan Franchini <twitch153@gentoo.org> (Sat 16 Aug 2014 09:00:47 PM PDT)

and original commit: 754cc935e1484
Suubject: Fix errors in overlay updates.
Author: Brian Dolbec <dolsen@gentoo.org> (Sat 26 Jul 2014 04:38:14 PM PDT)
updater.py: Adds list conversion for str conf_type