Add an ibus-table-setup to set ibus table engine

The setup app can be accessed from:
  ibus Preferences -> Input Method -> select a method -> Preferences

The code and ui were adapted from

 * ibus-setup-pinyin
 * https://github.com/maxiaojun/ibus-table-setup
Setup: Add table information to About page
Merge remote-tracking branch 'mozbugbox/ibus-setup-table' into ibus-setup-table
Left ALT key to cycle candidates in the current page
Catch exception when reading ~/.ibus/byo-tables so the process won't halt.
Merge remote-tracking branch 'anthonywong/master' into 1.6
Merge remote-tracking branch 'mozbugbox/ALT_L-cycle-candidates-in-page' into 1.6

Conflicts:
	engine/main.py
	engine/table.py