registry: update job when migrating legacy payload
systemd: log length of unit being written
agent: use correct Job object in LoadJob task

Fix #737
Merge pull request #738 from bcwaldon/737

Carry actual unit file into Agent LoadJob task
etcd: refactor TLS configuration

Separate reading files from creating a TLS config object.
Merge pull request #734 from bcwaldon/migrate-payload-job

registry: update job when migrating legacy payload
Merge pull request #731 from bcwaldon/refactor-etcd-tls

etcd: refactor TLS configuration
engine: remove superfluous state
Merge pull request #744 from jonboulle/fix

engine: remove superfluous state
engine: collapse Reconciler and dumbReconciler
engine: break out scheduler from reconciler
agent: move AbleToRun to AgentState
engine: drop offers; pick first capable agent
engine: refactor clusterState; track changes during reconcile
engine: schedule to agent with least number of units
engine: drop jobName from decision struct
engine: modify LoadedUnits when scheduling