Basic implementation of feature for ldap user synchronization as
background service. Introduced configuration property to configure the
synchronization period.
Fixed Tests, use local copy of users.conf. Initialize reset ldap before
every test.
Fixed error with negative periods. Using at least ldapCaching period to
sync with ldap
Load empty groups as empty teams from ldap, when ldap user
synchronization is enabled.
Documented default value for empty groups filter
Added logging for empty group sync.
API adjustments and elimination of duplicate config options
Fixed and introduced tests for synching ldap users and groups.

Using new settings key realm.ldap.synchronize
Switched from key String to Keys class. To avoid letting tests pass with
hardcoded keys wich doesn't exist anymore. Now on Key Refactorings the
test gets compile error again.
Test the isReady behavior from LdapSyncService.
Added LdapSyncServiceTest to GitBlitSuite.
Merged ticket #5 patchset 2