Whatsthis2

I added the 'whatsthis' function as a toolbutton in the MainWindow ( In the vacant slot in between the export button and the TEMPO/BPM window ). I found it a bit of a hazzle to dig into the menus to reach it.
Is this wanted?
![whatsthis](https://cloud.githubusercontent.com/assets/6368949/2871104/f0db3b8e-d2f2-11e3-9205-0722a040b104.png)