fix wording on failing test
remove quantity attribute and replace with "plural" flag - see issue #151
remove attributes from game date where they're the same as defaults (note boolean attributes must always default to false)
remove more default attributes (exits that aren't hidden don't need attribute set)
oops - almost ruined locations with hidden exits
remove a few more redundant attributes from data file
fix failing test around exit attributes.
migrate "money" to inventory object in advance of support for artefacts.
add cash status to inventory rather than status.
add support for money as an attribute of creatures so that they can start with money.  see issue #37
Add support for "buy" from non-creatures. Finish the vending machine implementation ( issue #149 )
minor wording tweaks to "sells" description.