option to get/set dates with a format.

[Rouche]

so the exchange between server and client can be forced to one format independently from the ui format. Usefull for automatic JSON serialisation withn Spring for example.

usage :

$('#div').multiDatesPicker({ addFormattedDates : [ ['2015-05-12'], 'yymmdd'] });

Ack the merge view is all screwed up! How come!