state: make InferEndpoints take varargs

Most of the callers, usually the tests, were having to construct a []string, just to satisfy the contract of the method.

Make the method take a varargs ...string which is consistent with other Relation methods.
Added versions to Agent API.
Added forgotten params.
Merge branch 'master' of https://github.com/juju/juju into agent-api-new-version-for-networker
Merge branch 'master' of https://github.com/juju/juju into agent-api-new-version-for-networker
Added new status format option: oneline to list units & their subordinates.
Revert "Added new status format option: oneline to list units & their subordinates."

This reverts commit 6841d5c80f68bbfc36da088f2d9c987300c64b1f.
Merge branch 'master' of https://github.com/juju/juju
Added new status format option: oneline to list units & their subordinates.
Support for new status formatter: tabular.
Migrated formatter to its own file. Refactoring.
Migrated formatter to its own file. Refactoring.
Merge branch 'master' of https://github.com/juju/juju
Wire up placement directives to EnsureAvailability api
Fix facade version detection
Code revew fixes
Rework how support for legacy installs is handled
state: remove unused return value from backingDoc.remove
Fix client fallback
Merge branch 'master' of https://github.com/juju/juju into agent-api-new-version-for-networker