add method to pickle the jobs as it necessary to working in JobsTable

the JobsTable use a multiprocessing manager. so the objects managed by
JobsTable must be pickle able. but the object from mongokit are not
natively pickable.
add statestate method to unpickle job

the Job object are pickle and unpickle when they are put and pop into or
from the JobsTable.
but the connection caaanot be pickable so the __getstate__ method say to
python how tom pickle them
the method __setstate__ add Connection, da and collection to the Job
instances