Moved all scheduling related functionality.

This adds a new plugin Sabre\CalDAV\Schedule\Plugin, and is the first
step towards calendar-auto-schedule support.
Added an inbox node.
Moved scheduling properties to the scheduling plugin.
Typo.
Correcting typo in getFeatures on auto schedule plugin

calendar-auth-schedule to calendar-auto-schedule
Merge pull request #356 from bretten/patch-1

Correcting typo in getFeatures on auto schedule plugin
A bit more documentation.
Merge branch 'calendar-auto-schedule' of github.com:fruux/sabre-dav into calendar-auto-schedule
Finding attendees.
Sending emails when inviting attendees.
Correcting typo in getFeatures on auto schedule plugin

calendar-auth-schedule to calendar-auto-schedule
A bit more documentation.
Finding attendees.
Sending emails when inviting attendees.
Merge branch 'master' into calendar-auto-schedule
Merge branch 'calendar-auto-schedule' of ssh://github.com/bretten/sabre-dav into calendar-auto-schedule
Adding Inbox getChildren, SchedulingMessage, and associated database table
Merge pull request #361 from bretten/calendar-auto-schedule

Calendar auto schedule
Merge branch 'master' into calendar-auto-schedule
Unittests are passing.