New configuration columns

Introduces five new slots to hold the various shortcut keys used
throughout the add-on.
Split off the generation of shortcut buttons

This will enable the re-use of this logic in a future bit of code for
assigning the new launcher configurations.
Enable configurator to update launch_ options

This makes use of the new "factory" method and adds a new "windows" tab.
Add disclaimer to the windows tab

This talks about when shortcuts become effective and that shortcuts may
not work if they are duplicated by other add-ons.
Use key_combo_desc as appropriate

Instead of deriving it using the crazy way Qt has, we can use the helper
function.
Wire up new shortcut functionality

All windows now launch by their configured keystrokes.
Remove default shortcut for browser stripper

Ctrl + Alt + T is actually already reserved by Anki, and this would be
an infrequently-used function anyway.
Prevent awesometts_pending crash

This could happen if no key had ever been hit before unpressing the
button, which meant that awesometts_pending would be uninitialized. This
can done during the factory method, though.
Various fixes for keyPress/keyRelease

Fixes the super call from keyRelease to actually call keyRelease on the
parent instead of keyPress.

Also ignores enter/return on keyRelease if there are buttons active so
as to avoid immediately disengaging a shortcut button if it was
activated in the first place by enter/return.