[TIMOB-14396] Tab icon/activeIcon Fixes

PR for [TIMOB-14936](https://jira.appcelerator.org/browse/TIMOB-14936)

Test is in [JIRA](https://jira.appcelerator.org/browse/TIMOB-14936?focusedCommentId=268309&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-268309)

1. New property on tabGroup - tabsTintColor
2. icon and activeIcon can now be specified to be rendered in original or template mode on IOS7+. Properties iconIsTemplate, activeIconIsTemplate. Default - true

Known Issue:
1. On IOS7+ activeTabIconTint property of tabGroup is not being honored. No idea why. tabsTintColor seems to work better (though it tints the title as well and works on active tab only though the docs say it should apply to all tabs.)

Docs will be updated along with the windowRefactor doc PR.