Add a plugin that displays the remaining battery power in %. This also
introduces the concept of arguments that can be passed to a module
during startup by delimiting the module name with ":", for example:
-m battery:BAT1 to query the BAT1 device.
Note that this works to an arbitray length, i.e. if a module accepts 3
parameters: -m <modulename>:<A>:<B>:<C>
The module gets the arguments as list.
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.
