Extract out the servlet environment.
Move to building a servlet context handler.
Fully extract the servlet environment.
Extract out JerseyEnvironment.
Fully extract the lifecycle environment.
Move context parameters to ServletEnvironment.
Move session handlers to ServletEnvironment.
Extracted admin stuff to AdminEnvironment.

This also allows for add arbitrary servlets to the admin interface.

Closes #259.
Drop the environment logger.
Added tests for ServletEnvironment.
Add some tests and some executor builders.