long-term updates

core_int - adjusted intersecting radius to 3 km, now use distance
function instead of Cartesian distance
date_interp_shalllow - adjusted nomenclature, added minimum depth of
undated reflection
date_interp - adjusted nomenclature
date_layers - changed elev_surf-elev_bed to thick, moved various
variables around, added new constraints, added Nye normalization test
prior to 2-D gridding, fixed how age uncertainties of core-intersecting
reflections are calculated, added depth uncertainty, added age/depth
uncertainty gridding
date_quasi_nye (formerly date_strain)
sloppy - adjusted loop ranges
strain_layers - dropped gimp from positions, adjusted number of inputs
check
traverse_merge - added time to saving
xy_int / xy_int_accum - keep lat/lon too