removal of GIMP ambiguity

aresp - adjustment of nomenclature and simplification of code
radblockproc - made block numbers > 99 work better, improved distance
calculation (now using MATLAB’s distance), removed option of GIMP for
Greenland (now it is the only option)
pickgui - adjusted ARESP limits, removed GIMP ambiguity, simplified
color scale adjustments
mergegui - removed GIMP ambiguity, simplified color scale adjustments
fencegui - removed GIMP ambiguity