Bug 1491: Adding an action to perform an absolute threshold

.gitattributes

.../include/AOFlagger/gui/strategyframes/absthresholdframe.h

...ger/include/AOFlagger/gui/strategyframes/iterationframe.h

.../include/AOFlagger/gui/strategyframes/sumthresholdframe.h

...r/include/AOFlagger/strategy/actions/absthresholdaction.h

...DP3/AOFlagger/include/AOFlagger/strategy/actions/action.h

...agger/include/AOFlagger/strategy/control/strategyreader.h

...agger/include/AOFlagger/strategy/control/strategywriter.h

CEP/DP3/AOFlagger/include/AOFlagger/strategy/control/types.h

CEP/DP3/AOFlagger/src/gui/editstrategywindow.cpp

CEP/DP3/AOFlagger/src/strategy/control/actionfactory.cpp

CEP/DP3/AOFlagger/src/strategy/control/strategyreader.cpp

CEP/DP3/AOFlagger/src/strategy/control/strategywriter.cpp