remove 'pool for window size change' functionality from terminal view flipper as current minimum is 9

feature offered after Android 6.0 (API 23)

remove work-around for 'pre-Eclair (android < 5) default implementation of onKeyDown()' as current minimum is 9

(also remove unused intent creation code)

Note it is depricated in API level 3 and current minimum is API level 9.

(hard-coded AddShortcut activity was replaced by new one based on resources)

(also rewrite code to be more readable)

(only in public methods)

This reverts commit 2f5d6e4b