clean mobyle2.exec_engine project tree

rename test directory as in mobyle2.lib project

remove:
 mobyle/core/jobref.py
 mobyle/core/mobyle_error.py
as the content is now in mobyle2.lib
remove module which not exists anymore in the package from __all_
replace old script to simulate job in fake DB by new one using mongodb

fill_db is replaced by sim_submission to put new jobs in mongodb as the
portal should do

check_db is update to print the content of jobs collection in mongodb
move the mobyle.exec_engine in Master as they need a config before to do
these imports

add argparse
   to provide option -c to specify a config file to start, stop or relaod deamon
	 to parse the argument (only start,stop,reload are allowed)

use the config object to retrieve where to store the pid file
use mongokit instead of mock in fake DB

- db_manager get and save jobs from mongo instead of pickling them in file
- status_actor.py, submit_actor.py update import according to new Status
	module location and update method to new Status object
- add build_actor to handle the job preparation (creation of working
	directory ...)
- monitor add case to manage job with buildable status
update script to simulate jobs submission

add new scripts:
- sim_submission which simulate a portal which add jobs in
  the DB (500 jobs randomly choose, the interval between 2 jobs vary from
  0 to 5s)
- check_db which display a sumarry of all jobs in DB to check the state
	of them in DB
fix test_DBManager.test_get_new_jobs

test_DBManager.test_get_new_jobs is replaced by
test_DBManager.test_get_active_jobs as the method change in DBManager
and fix the code according the new behavior of this method