Fix shell visibility in Android

Shell was no longer made explicitly visible due to missing property name
translation.

Also minor fix in TabFolder (Fix #207

Change-Id: I63f3070cff51a8da7909fad0735d11601d82b156
Fix image property on Action.js

This image was no longer encoded, breaking the existing launcher app
(among other). This is only a quickfix, I will refactor the property
encoding very soon anyway.

Change-Id: I56a5525e0a6b5fc06c235d611df0faea5c5b7346