Remove some redundant arguments.

* Bitmessage arguments still duplicate.
* Dropped web_xxx (only http used now)
* Flag settings cleanup and refactors.
Next round of refactors and fixes.

* Moved default context values inside OpenBazaarContext.get_defaults()
* New OpenBazaarContext.create_default_instance() used now on test_transport.py
* When shutting down we now have a mutex to make sure two SIGTERM and SIGKILL don't
  call the application.shutdown() routine at the same time.
* style fixes.
multiple refactors (encapsulation, readability, modularity, pep8)

* Should fix test breakage.
* Stopping from the Web UI was broken.
Use BitMessage together with the context.
Converge with #780.