Refactored so PPWSrc is no longer hardcoded, Reset Facebook and Google+ buttons to be enabled by default

Heya Felipe,

I noticed one of my last pull requests inadvertently set the Facebook and Google+ buttons to be disabled by default, the first commit resets them to be enabled by default. On a side-note, i think the Facebook and Google keys can be removed from the last return statement in ppw.js.

The second commit introduces a method that works out the path to power-polygon so the hard-coded PPWSrc values can be removed from the code. I tested this by moving the talks directory from power-polygon into the document root of my web server and updating the javascript src accordingly.

Mazzel,

Martijn.