Added a try/except to catch missing html element
Changed network attribute to id for network

The id attribute works all the time, where the network attribute
only works if you are not referring to a master network.
Better usage counting

Now that we allow network recursion, a user could log in to multiple
nodes in the same period. If that happens, we want to add their usage
to the existing user object, rather than try to create a new object.
Node names are optional

In CloudTrax, node names are optional, so the CloudScraper code
tries to allow this. I originally wanted to use the node mac address
as the dictionary key for the nodes. This is not possible as the mac
address that is listed against the user is the wifi mac address, and
the mac address that is listed against the node is the ethernet mac
address. Unfortunately this means we must use the network name as a
dictionary key.
Add additional usage to user objects