Adds support for font resizing at run-time. Three new actions are
introduced:
* IncreaseFontSize - Increases current font size by 1.0
* DecreaseFontSize - Decreases current font size by 1.0
* ResetFontSize - Resets font size to that specified in the
configuration.
The stock config files have example configuration for each which should
match gnome-terminal. For convenience, the config entries are:
- { key: Key0, mods: Control, action: ResetFontSize }
- { key: Equals, mods: Control, action: IncreaseFontSize }
- { key: Subtract, mods: Control, action: DecreaseFontSize }