This version of the API shipped with Indigo 7.4.0 - check the API Version Chart to see what version of the API is available in which Indigo versions.
Added device property SupportsOnState with value of True to relay and dimmer class devices. This allows for device UI filtering using props.SupportsOnState, which will select all relays, dimmers, and sensors that have an on/off state.
Removed ability to execute embedded AppleScripts in actions and added conditional Python support to Triggers and Schedules. This is not an API or Indigo Object Model change, but if a plugins requires Indigo Server python conditional support they can set their ServerApiVersion to 2.2 and Indigo will only install/enable the plugin if the user is running Indigo 7.4.0+.