ADD: [mouse] support long click + full click/double/long support for 5 buttons

/cc @jmarshallnz @Montellese 
It's overly confusing because the current code itself developed into a ugly hack, probably dating from the time button translation was implemented.

The ACTION_MOUSE in MouseStat are not actually actions. They are "transformed" into keys by "| KEY_MOUSE" and indeed always go thru ButtonTranslator (see Application.cpp:3124)

Adding hacks on hacks is surely bad ;) I'll rewrite the whole stuff to make it readable...