CB-6837 Fix leaked window when hitting back button while alert being rendered

Keep track of the last AlertDialog showed.
The last dialog showed that is rendered while hitting back button it
causes a leaked window.
Instead of perform a full track of all dialogs created, only destroy the
last one showed, this fixes the problem.

close #122
Update .gitignore to ignore /framework/build and /node_modules
Fix --shared flag of create script (broke in recent gradle changes)