This adds a new option (offline_credentials_expiration) to the
[PAM] section of the sssd.conf

If the user does not perform an online authentication within the
timeout (in days), they will be denied auth once the timeout
passes.

Create and populate user directories on useradd, delete them on userdel

Fixes: #212

The LOCAL provider does not have a mechanism to load alternate
auth, access or chpass backends, nor does it make sense to do so.

This will throw a configuration error if these values are
specified (unless they are explicitly also set to 'local')

In sssd only local is a native mpg domain, and it is forced.
All other providers will have to unroll mpg users into a user/group pair of
entries in the db. This allows the provider to automatically establish if
the remote server provides mpg users w/o possibily conflicting manual
configurations on the client trying to force an mpg behavior where none
is provided.

We have converted to using dhash in place of btreemap everywhere
in the code.

Use this new utility call to ensure that the config file is safe
to read from.

Introduces a new option --debug-to-files which makes SSSD output its
debug information to a file instead of stderr, which is still the
default.

Also introduces a new confdb option debug_to_files which does the same,
but can be specified per-service in the config file.

The logfiles are stored in /var/log/sssd by default.

Changes the initscript to log to files by default.

This converts a great many configuration options to the new
standard format.

This reverts commit 8c50bd085c0efe5fde354deee2c8118887aae29d.

Amended: commit 1016af2b1b97ad4290ccce8fa462cc7e3c191b2e also made
use of the SYSLOG_ERROR() macro, so those portions of that code
also needed to be reverted.