Initial attempt towards x509 credentials.
Does this help?
Merge branch 'devel' into feature/credentials
revamp security credentials

Session now inherits saga.Session, credential was renamed to context, and inherits from saga.Context.
This solves the X509 support, and all other contexts types are also available now.
Credentials are not serialized into mongodb anymore.  Resource configs are also directly communicated to the worker threads and processes, which should clear the path for closing #163.
This will also work for gsissh.
Add "old-style" lrz resource config for testing purposes.
Merge branch 'feature/credentials' into feature/multicore-archer

Conflicts:
	src/radical/pilot/configs/lrz.json
	src/radical/pilot/controller/pilot_manager_controller.py