Allow changing toolbar icon and codes

[Helium314]

Customizing icons was already planned, will be implemented here.
Since people want ever more toolbar keys, and adding everything myself is annoying and makes the toolbar selection menu horribly long, I decided to add the code customization in the same menu.

What's missing

• actually saving the settings
• sanity check for the codes (using checkAndConvertCode)
• restriction of the EditText fields (either to numbers, or allow labels with processCode)
• disable ok button of key code not ok
• nicer key selection dialog
• readout of customized toolbar key codes
• testing
• strings for everything
• some dummy toolbar keys that are just for doing custom stuff (when people don't want to modify other keys)
• maybe find a way to show the size difference between holo and other icons when customizing icons

[Helium314]

I guess this is fine good enough now...