CLC-3965 - Added Ruby-Net-LDAP to Gemfile
CLC-3965 - Added LDAP connection settings
CLC-3965 - Added Canvas::Synchronization model, seeded canvas_synchronization table to store last guest user sync timestamp
CLC-3965 - Added Canvas::Ldap to query Guest OU in LDAP for updates and prepare for SIS User Import into Canvas
CLC-3965 - Added comments to Canvas::UserProvision concerning status as a dependency of the Add People tool
CLC-3965 - Setup cmdline script and Rake task - canvas:guest_user_sync
Merge pull request #2717 from redconfetti/CLC-3965-guest-refresh

CLC-3965 - Implement appropriate guest user refresh solution