Add trigger modes

TRIGGERS

So for supported trigger mode it seems we can have those correspondances:

• XI_PRM_TRG_SOFTWARE
  • IntTrig -> set for N frames
  • InTrigMulti -> set only for 1 frames, so client should call CtControl::startAcq() for each new frame
• XI_PRM_TRG_SELECTOR
  • ExtTrigSingle -> X_TRIG_SEL_FRAME_BURST_START
  • ExtTrigMult -> XTRIG_SEL_FRAME_START
  • ExtGate -> XTRIG_SEL_EXPOSURE_ACTIVE