Blockify ui

Hi Mikar,

I did some pretty substantial cleaning up, I've included:

* A repeat in the reworking of functions
* Quite a few comments about the place
* Grouped the functions in a step by step manner
* Compressed some of the window grabbing functions together
* Reintroduced the toggle_mute, which means that it doesn't need to be handled elsewhere
* Reworded the readme, and changed the headings to h2
* Removed the need to restart blockify when adding a song
* Restored UI to how it was, it should all work as expected
 * Fixed the fixme that you mentioned

I think the comments throughout the code will really help anyone to reading it.