Fixes issue #1: on ROMs that draw hide-keyboard and switch-keyboard
buttons at the bottom of the screen, ReteKey drew its bottom row
underneath them, and those keys could not be pressed at all. The band
the system takes taps in is now left alone - and only in the navigation
modes that actually use it, so gesture navigation loses no height.

Two new layouts, off until you turn them on in settings: Arrows and
Keypad, on the 12-key frame.

Holding a 12-key pad now types a calculator's characters rather than the
digit: + ( ) - = % / e ^ across the pad, $ under the last vowel, ! and @
either side. The digits are still a tap away under 123 and on the new
Keypad layout.

Key captions and layout names are in English with the Hangul alongside -
2beolsik(2벌식), Cheonjiin(천지인), Naratgeul(나랏글) - and the pads say
Move and Next. The 漢 key leaves the 12-key pads; holding the layout key
still converts, as does the menu page.
