Changed bypassHandler related methods to static

The methods to manipulate the bypassHandlers list were instance methods, which means you have to have an instance of TriggerHandler to touch them.

It's a reasonable expectation to be able to bypass a trigger without being in a TriggerHandler, or instantiating one on the spot.

Now instead of this.bypass('SObjectTriggerHandler') or new TriggerHandler().bypass('SObjectTriggerHandler') you can use TriggerHandler.bypass('SObjectTriggerHandler') from anywhere