Starter, mostly stub code for issue #207.
Add data model for task/event scheduler.
Implement task dispatcher that is like crond to poll for scheduled events every
minute and dispatch those events to task workers. Integrate this framework into
smart manager damon.
Implement the rest API for event/task scheduler.
Add event scheduler config parameters to buildout
Implement CLI support for event scheduling.
Update service model to include service config metadata.
Update prepdb to include nis as a registered service.
Add packages needed for nis to buildout.
Add low level nis configuration code.
Add nis to low level service automation.
Implement backend API for NIS. Refactor services API for better abstraction and
pagination support.
Implement CLI support for NIS.
Refactor service API to use base service view.
Update service API urls and deprecate ServiceView entirely.
Update CLI to conform to new services API.
Merge branch 'issue#210_nis' of https://github.com/schakrava/rockstor-core into schakrava-issue#210_nis

Conflicts:
	src/rockstor/smart_manager/views/__init__.py
	src/rockstor/urls.py
Merge pull request #209 from schakrava/issue#207_task_scheduler

Issue#207 task scheduler
Resolve migration file conflict as a result of merging latest changes from
master
Services

Change command url to POST with the command name as part
of the url