add functions for moving players between locations

Add Player.startMove and Player.endMove for handling player movement
between locations. These functions work purely on the model (or "game
logic") layer, i.e. no dealing with various client request types or
reconnecting to different game servers.
Nevertheless, the division in two separate steps here does correspond to
the actual move process flow between client and game server(s).
add handling of login and logout requests

* add core request processing mechanism: forward requests to GSJS
  request handler function, and add special handling for particular
  request types before and after that
* add basic player login and logout handling, based on knowledge gained
  with throwaway server prototype; TODOs in several places where other
  parts of GS functionality are still missing
docs typo
change default config for tests to worker process

change configuration for unit/functional tests to behave as a worker
GS process, since that is what most tests will likely need as a basis
(can be overridden if necessary)
tests around player login/logout

* functional tests do not actually invoke the GSJS request
  processing routine yet (would just cause errors due to missing API
  functions)
* functional tests for login_start/login_end are somewhat fragile
  and might have to be reworked or removed, if they end up causing
  too much trouble
add support function for moves between different GSs
remove player and related objects on disconnect

* includes an item management function in the Bag class (which is
  required to retrieve the player inventory)
Merge pull request #7 from yelworc/login-logout

player movement between locations and login/logout