Added doxygen comments to PolyUITextInput.h
Added tagfile generation to doxygen files.

This enables links between modules, by generating a tagfile when module A is generated, and using that tagfile when generating module B.

See also http://stackoverflow.com/questions/8247189/doxygen-is-slow/8247993#8247993
Fixed the doxygen string for UITextInput::insertLine
Merge pull request #249 from CIB/documentation

Doxygen stuff