-Added sync: resets the beat and bar

This is a stepping stone to making the user master of rather than a slave to the the metronome  and eventually adding feature #65. :smile: 

Only started reading the code today so I am not sure I have understood all the repercussions of what I have done but it does seem to work.

Not sure how you feel about the GUI placement either. I am not set on that: just did the quickest thing by squeezing it in where it is.