make writeDir

if you didn't set up the folder you want to save in, it is automatically
created
Changed ROI data structure.

Changed ROI data structure to be safer to maintain. Information specific
to a particular ROI is now all stored in an array of structures with
nRoi elements and the fields "id", "group", "indBody", "indNeuropil" and
"subCoef". ID is a unique identifier for a given ROI that is never
re-used even if the ROI is deleted. selectROIs and extractROIsBin have
been updated, and a conversion function for existing acquisitions has
been added to the auxiliary function folder.
Merge remote-tracking branch 'origin/master' into ari