fix typo
MXGDA-830 add allowUseOfPreviousScanSettings

Conflicts:
	uk.ac.gda.api/src/gda/scan/ScanPlotSettings.java
MXGDA-830 check plot settings whether to use previous settings
MXGDA-830 add set preference RCPController command
MXGDA-830 make XYPlotView respond to autohide preference changes