Added filter decorators for tests

When you pass a noun filter phrase to a test, the filter decorator will
translate it into a list of nouns and pass that back to the method.

Stored in a separate module so these can also be imported into actions.
Yes, I know I'm getting ahead of myself, but I know I'll be using these
in actions and besides, I couldn't resist.
Finished adding tests, added unit tests for actions

All tests in the current Adventure Engine API have been implemented, and
all the actions have at least one unit test set up (even if empty).
Noun and room descriptions, object filters

"Object" meaning "noun or room".
Replaced filters with selectors

The decorator is passed the types of selectors that will be used as
arguments for the test or action.

Also, this new implementation has unit tests! Yay!
Added some actions, and some state methods for nouns

Noun movement actions have been added.

Hit a bit of a snag because state methods were taking arbitrary numbers
of arguments, but now some methods have been added that take two types
of arguments (nouns and locations), and it's not possible to do
arbitrary with both. So with these, the last one can still take
arbitrary numbers.

Also, the message action now takes multiple arguments; made this change
in starflight.json.