Pass the "output" object to the modules' constructor to allow them to
define their own callbacks.
Any user-provided callbacks take precedence and override those of the
module.
The i3 output now has a separate thread that continuously monitors stdin
for incoming click events. The generic output class also has methods for
registering callbacks (as commands). For now, by default, scroll events
will be used to emulate the next/previous workspace.
It is now possible to add a list of theme configurations in the
"default" section called "cycle". These configuration items will be
cycled through module by module. to create "alternate style" effects.
This is *only* possible in the "default" configuration part, but any
module-specific configurations still take precedence.
Also, removed the capability of per-widget themes. That simply
complicates things and probably doesn't really bring any benefits.
Add - again a very simplistic - method for themeing the output.
Essentially, the plan is to have JSON-formatted configuration files in
bumblebee/themes/ and have a separate class for querying the config
whenever the output needs to know about semantic formatting/coloring.
Note that the theme object is stored on a per-module basis. Right now,
that doesn't have any effect (except looking particularly wasteful), but
the idea is to be able to have different themes for different modules in
the future.
