Add YAML metadata file for docker sensor.
Add YAML metadata file for git and jira sensor.
Add YAML metadata files for sensors in aws pack.
Update docker sensor so it implements "poll" method which is required by the new
StackStorm versions.
Update rest of the sensors to implement poll method.
poll -> run.
Update sensor classes so they work with the new class hierarchy.

Note: This makes them incompatible with StackStorm v0.5.
dispatcher -> sensor_service.
Return instead of continue
YAML lint fix
Merge pull request #55 from StackStorm/sensor_sandboxing_changes

RFR: Sensor sandboxing changes