Add "chains" to represent runner-target relationships between Agents.
Provide a target agent select box for an agent that can run other agents.
Show target-runner relationships in a diagram.
Add SchedulerAgent, which periodically runs other agents.
Add a spec for how the before_save hook should work.
Store an agent ID in the local storage rather than stashing it in a tag.
Fix the schema version.
Rename "runner" to "controller".

This is done in preparation for adding an ability for an agent to
enable or disable other agents other than running.
Improve the description.
Disable second precision schedule by default to prevent service abuse.
Add control action types "enable" and "disable".
Use error for error, not log.
Merge branch 'master' into scheduler_agent

Conflicts:
	app/helpers/agent_helper.rb
	db/schema.rb
Fix specs for the new stuff in DOT output.
Rename "target" to "control target".
Merge remote-tracking branch 'origin/master' into scheduler_agent
Fix a bug with edge line styling.
Rename "chain" to "control link" for clarity.
Allow multiples of fifteen as seconds.
Compare user_id's rather than user objects.