Checkpoint for collaboration

The leadership service endpoints have been defined so that others can begin writing against the API. Currently everything else is stubbed out.
Merge branch 'master' into leadership
move context inside runner -- integration tests still passing, nothing else even checked
fix context package tests
fix uniter/operation tests
rename uniter/context to uniter/runner
Regenerate state server certificate to update SAN attribute with machine IP addresses
Merge branch 'master' into uniter-deemphasise-context
added support for setting metric credentials on the service

removed credentials from metric to metricBatch
Addresses are added to certificate, and consistency checks required when saving
renamed updatemetriccreds to set, added test, other review comments
Implemented changes from reviews.

- Mostly godoc tautological comments.
- Reorganized imports.
- Moved params from apiserver/leadership to apiserver/params namespace.
- Removed bulk oriented calls from client API as they are not yet needed.
- Annotated errors from making facade calls in the client API.
- Now checking that stubbed-out functions are being called.
- Now checking that service and unit tags are correct.
- Cleaned up error messages.
- Upon starting, the lease manager was not checking existing leases for expiration.
- Giving the lease expiration test slightly more wiggle-room in regards to timing.
- Added TODO in state.go to reflect that leasemanager should eventually be peeled off.
- Added tests to the apiserver layer to test authorizer errors.
Block all changes.
Added user commands and refactored common code for readbility
No need to store sevrer cert in state - it is generated on each state server
Added authorized keys blocking.
Added trace errors where appropriate.
Fixed comments as per review feedback.
Added unit-tests for authentication.

There were previously no unit-tests for the apiHandler which provides authentication for most service endpoints. These tests were previously implicit in the full-stack integration tests which were usually performed.
Block all changes.