Improve file reading for trial parameters file

[bartnijssen]

https://github.com/NCAR/summa/blob/develop/build/source/engine/read_param.f90#L175-L182

Currently the code has a hard wired name for the variable describing the hru ID (hruId), but this is actually different than what is in the test suite (which uses hruIndex). I think that actually means that the index in the file is not used and the code should not continue in that case, because the default is to "expect HRUs to be in the same order as the local attributes". However, the user may not have full control over this in NetCDF files and there is no reason to make this assumption. The risk here is that hru and gru attributes are assigned to the wrong hrus and grus.

We should require a specific index variable (for example hruId and gruId and then use these values to map the values to the correct HRUs and GRUs rather than relying on an assumed order. If the index variable is not present, then the program should FAIL.

[bartnijssen]

See also #253 : The part in common is that we do not search for the correct hruId