Dropped creation of delta_dimension and delta_units for units without offset
Dropped creation of delta_dimension and delta_units for units without offset

The dimension delta_temperature was dropped because having two dimensions
for temperature has no benefit but only complicates the implementation of
calculations with quantities that have an offset unit. For temperature,
delta_kelvin and delta_degR do no longer exist. There are now only two
delta_units left, delta_degC and delta_degF, which are also of dimension
"temperature".

dmwelch/pint