Commit the db session at the start of celery tasks
Separate tags by spaces, not commas in filter

This is more consistent with how it's done in the job view.
Require all tags in filter (logical "and")

This changes the job filter behavior from listing all jobs that have any
of the requested tags to only listing jobs that have all of them.

That was the intended behavior from the start, the old behavior was a
bug.
Display tags inline next to title

instead of in their own columns.  Also, the tags are clickable now.
Fix regression when no tags filters present
Allow specifying dependencies for a job in API

As "parents"
Don't assign agents to job with unmet dependencies
Support parents/children in relationship unpacking
Show job parents/children in UI, if present
Don't reraise exception on unreachable agent

Reraising the exception at this points tends to clutter the log with
lengthy backtraces, especially in farms where many agents are not online
all the time.  Technically, the celery task was successful in that case,
too: The agent was polled, and found to be offline.
Bugfix: Use _WorkState instead of WorkState

"parent.state != WorkState.DONE" ended up never evaluating as true.
Merge pull request #241 from guidow/commit_session_in_tasks

Commit the db session at the start of celery tasks
Merge pull request #243 from guidow/tags_work

Tags work
Merge pull request #246 from guidow/dont_reraise_unreachable_agent_exception

Don't reraise exception on unreachable agent
Merge pull request #244 from guidow/job_dependencies_fixes

Job dependencies fixes