new functionality: depth view, mouse-click layer selection

core_int - corrected DYE-3 longitude
pickgui_man - updated to be in line with recent changes
fencegui - depth view (unflattened); mouse-click layer selection; some
variable/function name changing
mergegui - depth view (unflattened), eliminated merging of
non-essential variables; some re-naming of functions and
simplification; mouse-click layer selection
phaseinterp - homogenization of behavior, got rid of temporary
debugging code
pickgui - depth view (unflattened); semi-auto picking simplification;
view homogenization
radblockproc - fixed bug where aircraft elevation and measurement time
weren’t getting trimmed when NaN’s present in position