Introduce onReady callback option to translate editor

Can be used for any kind of UI customization

Change-Id: Ifdac69e82fc270412158f66da48709197873e139
TranslationStash: Customize the skip button text to 'Try another'

Change-Id: I241e4bab4ec967e6c7ddf7b3d1ce4f7c893a55e1
Merge changes I241e4bab,Ifdac69e8

* changes:
  TranslationStash: Customize the skip button text to 'Try another'
  Introduce onReady callback option to translate editor