[TIMOB-17818] make exitOnClose settable at any time

Conflicts:
	android/modules/ui/src/java/ti/modules/titanium/ui/TabGroupProxy.java
[TIMOB-17818] fixing doc issue
Merge pull request #6264 from jonalter/TIMOB-17818-3_4_X

[TIMOB-17818] 3_4_X make exitOnClose settable at any time