NDPluginROIStat: add in Reset and ResetAll records and parameters. The Reset record will reset the ROI data for one ROI. The ResetAll will clear the data for all the ROIs.
NDPluginROIStat: implement ROI specific reset.
NDPluginROIStat: remove setting NDArraySize params, as these don't apply to this plugin.
NDPluginROIStat: move reset logic into function.
NDPluginROIStat: tidy up writeInt32 function error handling.
NDPluginROIStat: implement ResetAll logic. Tested ok with multiple ROIs.