Handle invalid time slices in netCDF/CF files

We ran into an issue with some netCDF files in the CF convention where
ParaView was not recognizing the time dimension. The problem was not so
much that the reader did not identify the dimension as time, but that
the time values for the last several steps was 0 because there was
garbage written in those time steps. The reader blindly appended those
time values and then gave an invalid time range. ParaView saw the
invalid time range and decided the data had no time.

To solve this issue, the netCDF reader now identifies time values that
are not in sequence and removes those out of sequence time slices.