Fix #49: Add function for alt attribute of input node
Enhance accessor for alt attribute of input node: Return empty string if attribute is absent and the input type is not image.
Merge remote-tracking branch 'origin/master' into bug/imagebutton-alt

Conflicts:
	packages/HTML.package/monticello.meta/version
Merge pull request #52 from SWTI2014/bug/imagebutton-alt

Fix #49: Add function for alt attribute of input node