add a REPL interface for debugging

This adds a REPL interface to the worker processes (reachable via TCP
socket) that exposes access to the GSJS admin object, the global model
API and the persistence layer. A simple client is also included (start
via `npm -s run repl`).
make stacktrace length limit configurable
prevent error on furniture bag deletion

Somewhere during player.adminResetPlayer, all the player's existing
furniture items are deleted; in that process, the item's isOwner
function is called, which fails because at that point the item
container has already been removed.
This change prevents that isOwner call.
add API function for moving offline players

(used during player.adminResetPlayer)
make apiDelete a GameObject API function

The docs only mention apiDelete for items, but GSJS code actually calls
it for groups, quests and locations too (e.g. while cleaning up quests
during player reset).
add GS RPC function 'resetPlayer'

* add GS RPC function for resetting existing players; this could be
  included in the webapp, so alpha testers can fix certain problems
  themselves
* the change in objrefProxy enables better error log messages for
  invalid objrefs with the rethink persistence back-end (including the
  broken TSID)
* unrelated drive by commit: API function global.apiNewOrderedHash
Merge pull request #45 from yelworc/debug-repl

add debugging REPL
Merge pull request #46 from yelworc/trello#39_player-reset

player reset function