Bug 906096 - Move InputMethod API behind a pref instead of build option. r=kchen, r=sicking

--HG--
rename : b2g/components/Keyboard.jsm => dom/inputmethod/Keyboard.jsm
rename : b2g/components/MozKeyboard.js => dom/inputmethod/MozKeyboard.js
Bug 909124 - [b2g desktop] shell.js did not get correct mozbrowserloadstart event to send Gaia the pending chromeEvents. r=fabrice