Reorganiaztion of Kupfer's python modules

[Ulrik Sverdrup <ulrik sverdrup gmail com>]

Hi,

I want to do an internal reorganization of kupfer's python package.

Internally we should group modules into subpackages. I have a draft of
this in the reorganization-wip branch on github. This reorganization
is mainly a refactoring so that very big modules (data, browser and
objects) can be split into smaller parts.

I have proposed the following:

kupfer.core -- modules data, search relevance etc. Kupfer's engine.
kupfer.ui -- user interface (browser, keybindings, d-bus, preferences)
kupfer.obj -- All KupferObject related stuff, and tools for those

Since before we have the subpackage kupfer.plugin for all plugins

Remaining in kupfer.* are modules that are used in more than one of
these subpackages.

The packages kupfer.core and kupfer.ui are naturally out of bounds for
Plugins. These limits are now much easier to see; in practice, plugins
should be able to use anything in kupfer.* or kupfer.obj.*  (even
though there are some exceptions).

We can keep stub objects.py and helplib.py to support compatibility
for custom user plugins. Does anyone think this is needed? (If someone
has a good plugin they should contribute it..). Also, by far the
largest change is adapting all plugin imports to the new organization.

Any feedback or suggestions on the reorganization?

Ulrik