Relaxed cross-origin headers to allow all origins in order to make...

...requests from other domains.  I also added the OPTIONS endpoint to
user.py because I guess when Ajax makes a request with a custom header,
it first sends an OPTIONS preflight request.  I added this endpoint to
allow that to work.
Changes to support many recent cosmology use cases...

clients/python/girderClient.py: a python class for interacting
with the Girder REST api

girder/api/api_main.py: changed to load in a new hacked REST class

girder/api/v1/file.py: changed to allow uploading a file to an
existing item

girder/api/v1/item.py: had to add an OPTIONS method so that my js app
could PUT metadata on an item

girder/api/v1/remoteconnection.py: a hacked REST class to show an
example of how I would like to extend Girder REST api

girder/models/item.py: catching this exception allowed me to figure
out that the character '.' is not allowed in metadata keys

girder/models/upload.py: another hack to support uploading a file to
an existing item

girder/utility/server.py: added a line so that another machine could
connect to Girder, otherwise only localhost was allowed