Overrides had no "cp", the connection was named uep

Updated Overrides to get a new connection from the provider
every time, this will avoid holding on to stale connections
in places like managergui, where the Overrides object is
created in the gui constructor.
Merge pull request #936 from candlepin/ckozak/fix_repo_overrides

Overrides had no "cp", the connection was named uep
Fix yum subman plugin RepoActionInvoker error.

RepoActionInvoker uses a injected uep, we don't
need to pass it as an arg. Leave the try/except
wrapped creation of one here to determine
if we have certificate issues.
Merge pull request #934 from candlepin/alikins/fix_yum_plugin

Fix yum subman plugin RepoActionInvoker error.
1094492: Consumer name length issues in certificate

We were using the type 'directoryName' for SubjectAlternativeName.
It has a size limit that is less than the 255 we use to constrain the
consumer name. Will use type 'uniformResourceIdentifier' instead.
Neither is used as per the type [the starting tag is stripped anyway].
1095938: re-add at-spi locator in repos window
Merge pull request #938 from candlepin/ckozak/atspi_repos

1095938: re-add at-spi locator in repos window
Merge pull request #937 from candlepin/wottop/1094492

1094492: Consumer name length issues in certificate
Add ContentActionClient

Replace RepoActionInvoker in main ActionClient with a
ContentActionClient.

Split BaseActionClient to its own module.
Add ostree_action_invoker (ostree repo action)

Hook it up into ContentActionClient
Add ContentActionPluginConduit plugin.

This conduit is for plugins that will add
content actions used in ContentActionClient.

Rev plugin api version to '1.1' since this is
a backwards compatible change. And I remembered.
Add a dummy yum_content plugin for testing
Load content actions from plugin class search

The content action client, now uses the subscription
manager plugin hook 'content_plugin_search' to find
ContentActionInvoker style classes, construct them,
and add them to the list that ContentActionClient
will run.
Replace odd usage of 'repolib' name.

This code actually passes a RepoActionInvoker now,
so remove the confusing repolib name.
entcertlib.repo_hook can be content type agnostic

More than likely, we can remove this tightly coupled
if we make sure entcert updates are via an ActionClient
that will follow up and update content.
Add test for ContentActionPluginConduit
Hit ContentActionClient for some test coverage.

It's tests need to get split out at some point.
Remove sample yum_content plugin

It will re emerge as ostree plugin in
src/content_plugins/ostree
Add content_plugins dir,and ostree content plugins
HACK: install ostree content plugin in site-packages

/usr/share/rhsm-plugins/ is not on sys.path, so without
append to path, we can't include submodules there.

Plugins can install their helper modules to standard
python paths. At the moment, hardcode
/usr/lib/python2.7/site-packages/rhsm_content_plugins

Need to generalize that. Plugins may need their
own install process. But this get's things testable.