pkg: trigger reconciler on start up
agent: add metadata validation for global units
Merge pull request #811 from jonboulle/811_agent_global_validation

global units: do some agent-level validation
fleetctl: unload should treat global units the same as other commands
agent: do not create UnloadUnit tasks when current state is nil
Merge pull request #853 from jonboulle/853

global units cannot be unloaded
Merge pull request #852 from jonboulle/trigger

reconcile: trigger immediately on start up
log: add EnableTimestamps
fleetctl: enable timestamp logging

Fix #847
log: manually construct header