Settings system. Now is probably the right moment to tell if you don't like it :)
Adopted modules to new settings system

Btw. nothing has changed for the config files. You can pass into
__init__ a dict as before, or you can use keyword arguments.

Either way, a module defines the settings that can be specified
and those which are required. __init__ basically checks that all
required options are set and that no invalid options are used.
Configuration shortcut

You can now pass a module (the Python thing, e.g. modsde) into register
and it will just "do the right thing" (find a class derived from Module
in that module and instanciate it with any extra arguments)
Fixed issue with standalone usage
Readme
.
StandaloneIO
Refactored the "find appropiate class" part a bit
Mail checkers

Mail checkers are not separate modules anymore; there is only one
mail checker module (called mail) that can make use of various backends
, which were formerly modules on their own.

This greatly simplifies code and reduces redundance.

This commit only contains the base classes for this.
Ported notmuchmail (needs testing)
Thunderbird
IMAP mailchecker
Renamed IMAP mail checker to … imap
modsde uses .format now
SettingsBase
Moving code around a bit
First draft of a doc generator for this

(Already supports multiple Modules per python module)
Docstrings
README
~rough refactoring