[SSSD] [sssd PR#188][opened] Add the first version of the KCM responder

[jhrozek]

   URL: https://github.com/SSSD/sssd/pull/188
Author: jhrozek
 Title: #188: Add the first version of the KCM responder
Action: opened

PR body:
"""
These patches add a new service for managing Kerberos credential patches. It
follows the design document here:
    https://fedorahosted.org/sssd/wiki/DesignDocs/KCM

So far all the credential caches are stored in memory. However, all the
internal APIs are ready for talking to sssd-secrets and store the caches
there which is what I'm working on now.

As per testing, it should be enough to set the default ccache name to
"KCM:" and make sure the sssd-kcm socket is enabled and started and the
sssd-kcm service is enabled.

It is important to test access control. Manually, I tested two different
UNIX users, tested setting the KRB5CCNAME variable to someone else's ccache
and so on, but more testing is welcome.
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/188/head:pr188
git checkout pr188