V2.3.1 Perpetual-Beta Release for public usage: Minor update to work with YouTube's front-end webpage code changes. Main player option moved to own setting

A small update with only a jump in the least-significant digit "v2.3.1". This represents a minor change to user experience and minor updates to the underlying code. This version updates to stay in line with the official add-ons release "v2.3.2" and represents changes keep in line with YouTube's code changes to the front-end browser elements and main player's switch to it's own setting. This version is identical to the source code in V2.3.2 on addons.mozilla.org.