Revert "Merge pull request #530 from ericsnowcurrently/backups-storage"

This reverts commit a93e1df919450377b6dab707552582fd604cd8cf, reversing
changes made to 7f3fa3837a32416736f6affd7c7bb530e8af3f00.
Revert "Merge pull request #607 from wallyworld/agent-version-on-startup-trunk"

This reverts commit 880aaa83f1a474ef7856f1237c3781ab6a51dbfe, reversing
changes made to 66b33ceb24eef4a4593d9ab52edcf5f55a25089a.
Merge pull request #609 from bz2/revert_breakage

Revert pull requests #530 and #607

The gating test job on master is currently broken, and let through two broken pull requests, #530 and #607. This branch reverts those landings to restore head to a buildable state.
action-set: a jujuc command for Actions to send values back to state

action-set permits action hooks to define an arbitrary map of params
which will be returned to the state server at the end of the Action.
action-set multiple invocation tests and panics fixed
action-set: a jujuc command for Actions to send values back to state

Addressed fwereade's concerns for PR 415.
action-set: a jujuc command for Actions to send values back to state

This commit moves the Action results update method into the Context
implementation, so that client code is not changing the results map
on its own.
action-set PR tweaks

Addressed:
 - need to keep Action results map segregated from jujuc
 - testing Context interface mock to support this change
 - removed old Context methods
 - changed actionResults inner "error" type to string rather than error
Now tests action results interleave in context