Adding support for trigger type in the Python API.
Adding support for trigger type in the Python API.

mit-crpg/openmc,amandalund/openmc,walshjon/openmc,shikhar413/openmc,shikhar413/openmc,smharper/openmc,smharper/openmc,mit-crpg/openmc,amandalund/openmc,liangjg/openmc,smharper/openmc,walshjon/openmc,amandalund/openmc,mit-crpg/openmc,paulromano/openmc,smharper/openmc,shikhar413/openmc,liangjg/openmc,paulromano/openmc,walshjon/openmc,mit-crpg/openmc,liangjg/openmc,paulromano/openmc,walshjon/openmc,paulromano/openmc,liangjg/openmc,shikhar413/openmc,amandalund/openmc