Added UIElement methods SetDeepEnabled / ResetDeepEnabled / IsDeepEnabled to allow setting enable on an element + all it's child elements / reset it to previous state.

Example usage: On scroll view, could disable all children while touch-scrolling to prevent accidental triggering of items.
Fixed a compile error with LUA.
Merge remote-tracking branch 'remotes/hdunderscore/UIElement_SetDeepEnabled'
Unify SetDeepEnabled() API between UI & Node. Removed IsDeepEnabled() function & "Is Deep Enabled" attribute as it may return different value than last SetDeepEnabled() and can not therefore serialize/deserialize accurately. Instead added IsEnabledSelf() which returns the enabled state before SetDeepEnabled(). Changed Node::SetEnabled(bool, bool) to SetEnabledRecursive(). Unlike SetDeepEnabled() it does not preserve node's self enabled state. Added AngelScript binding for SetDeepEnabled operations.