conntrack: change parent class of Bitmask

from object to int to fit with Conntrack.set_attr()
conntrack: set default mapfile at labelmap constructor

using kwargs.
examples: nfct-daemon

change unit to bit per second.
conntrack: fix unneeded byref
conntrack: remove unnecessary tailing comma
Revert "conntrack: change parent class of Bitmask"

This reverts commit d751d113d15d16b8489d5677463b7923779e3afd.
conntrack: update to pass Bitmask to set_attr()

It seems a little messy, sorry.
examples: added

nfexp examples are suspicious...