Move central constant definitions into __init__.py. This does away
with version.py which contained nothing else and __init__.py is where
things like __VERSION__ are usually defined.
This commit also changes code to use offlineimap.__version__ rather
than offlineimap.version.__version__ as was before. Cleaned up some
duplicate or unneeded imports while touching those, formatting import
statements per PEP8 (one import per row).
Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>
