ENYO-2255: put back dissolve div on respective tab

dissolve position is relative to onyx-tab-item. Hence onyx-tab-item must
have a position statement to create a new context
ENYO-2255: removed less cruft (css less that is)
ENYO-2255: fix data structure sent with event
ENYO-2255: fixed gradient on IE-10
ENYO-2255: recompiled onyx.css