Some fixes for Youtube polymer engine
As old layout engine for YouTube are now partially disabled, there is a script to fix some annoying things.
Settings are accessed through screwdriver and wrench icon at the header of page.
Currently inplemented options:
* collapse "guide" menu by default;
* smaller text size in video descriptions;
* smaller video thumbnails;
* hide suggestion blocks;
* constant video player size;
* align video player on the page;
* unstick header bar from top of the screen;
* hide channel banners;
* change YT logo target.
Settings are saved in YouTube's local storage, so it must be accessible in order to change them.
For FF 56 it translates to allowing cookies on YouTube.
Feedback and suggestions are welcomed (one suggestion/issue per thread, please).
