WIP: add a finder

Change-Id: Ifc9a858d4006bf5ff8ee5659651c5e82f2e5e71b
Bankruptcy commit from last few openhacks

Move all the code around, make tests actually pass, and do things.
Reasonable stuff from here on, I promise.

Change-Id: I6524fb39e8b38e5879065e1d9d94612b52c6e255
Pull out listings into its own class

Don't specify a default bank in the client, let another nerd deal with
that

Change-Id: I103e35daecb7574ce74694fbc69ed2b14f828ba2
Rename Hat to Marketable

Change-Id: I6b882b949deca764f4ea853ca9f06469ce7778d1
Pull out items into own class

Change-Id: Id239845ef47f0e19d5e5820892c1538655b3d86a
Not specifically unusual

The link fits any marketable

Change-Id: I40b3e9e42f36ee21bd7a71a12b837d8d4a07ed90