Add socket timeout to uri module.

The uri module can be configured to abort after a specified timeout if
it cannot connect to the configured uri. This prevents a uri action from
hanging indefinitely when the remote endpoint cannot be reached because
it is unavailable, there is a firewall in place etc. The default behavior
is left unchanged: timeout=None

This change also introduces a new type for module_parameters: int
Code was added to perform conversion from string -> int type in
module_common.py.

The new type was required in order to play nice with httplib2 which
refuses to accept (and convert) anything other than a numeric type for
the timeout value.