Add a command palette

[sspanak]

For easier access to functions on phones with few hardware buttons, it would be easier to invoke the respective functions with star+number combos, instead of with hotkeys. For example, #83 and #170 would require multiple key control keys.

Also, the hotkey processing is getting more and more complex, which is not the way to go.

To resolve this, add a command palette:

• Split TraditionalT9 class in three logical pieces.
  • TypingHandler extends KeyPadHandler. It contains 0-9, Ok and backspace processing code.
  • HotkeyHandler extends TypingHandler. It contains the hotkey code
    TraditionalT9 is on top and contains tools like getting the context and whatnot
• Add a "show commands" hotkey. It will display a numbered list of commands. Default key is: "*".
• Pressing a number when the command palette is on invokes the respective command.
• Command list: 1. Add word; 2. Show settings
• Remove the "Add Word" and "Show Settings" hotkeys.
• Make sure the command palette fits well, when the on-screen keyboard is on.
• Make the list touchable, so it can be used on a device without a hardware keypad.
• Remove Add word and settings handling from KeyPadHandler. Done in another issue.
• Make a migration for resetting the hotkeys There is no need to migrate anything. The old hotkeys will simply not exist.

[stianhoiland]

I suggest leaving in the Add Word and Show Settings hotkeys. It just increases the customizability available to people. Some people prefer weird things!

[sspanak]

Well, I suppose there is no harm in leaving the hotkeys.

[sspanak]

After all, I've decided to reduce the number of hotkeys to minimum to make the code simpler and easier to maintain. I believe the new command palette will be convenient enough to compensate for that.