core double click zoom support
added in the doublecliickzoom as an aoption and implemented it in all the completed control implementations. found and fixed a few control based bugs along the way.
Merge branch 'release-3.0-tile-layers-cleanup' of github.com:mapstraction/mxn into release-3.0-tile-layers-cleanup

Conflicts:
	source/mxn.core.js