Add support for Multi-Variate MODE

[dwfncar]

A new MODE tool is to be created to perform arbitrary set operations
(union, intersection, difference, etc.) on objects generated by MODE.
The objects in general will be associated with different variables.
Object attributes (centroid, axis, etc.) will be computed for the resultant objects.
Matching and merging may be a later option.
This tool is to be tested on fields relevant for dryline identification
(gradient of temperature, gradient of specific humidity, etc.).
The output format of the new tool will be identical to that of MODE.

Account Key: 2700042 WPC

Related METplus issue: dtcenter/METplus#1516

[JohnHalleyGotway]

Reopening this issue.

Merging in the multi-variate MODE PR into develop triggered a testing workflow run for METplus. But 6 of the 44 testing groups failed with runtime errors from MODE. So while the changes didn't break the MET regression tests, they did break the METplus ones.

All of the MODE runtime errors look something like this:

ERROR  : 
ERROR  : replace_env() -> unable to get value for environment variable "7??W?f?ʳ࿑5??ȕZ̈??ȗ&<y2?Ht???!̛*%Z4e?j"
ERROR  : 

Here's why... the logic on this line is insufficient:

const char * const user_config_filename = argv[3];

It assumes that the user-specified config file is always the 4-th item on the command line.

However, METplus runs MODE like this (at least in all of the failed runs):

bin/mode -v 2 /d1/projects/METplus/METplus_Data/met_test/data/sample_fcst/2005080700/wrfprs_ruc13_12.tm00_G212 /d1/projects/METplus/METplus_Data/met_test/data/sample_fcst/2005080712/wrfprs_ruc13_00.tm00_G212 MODEConfig_wrapped -outdir out

Having -v 2 immediately after the executable shifts the config file down. The weird error message is the result of trying to parse a binary GRIB file as if it were an ASCII config file. Rerunning the failed MODE command line with all optional args following the required ones fixes this problem.

However the real fix it to use the CommandLine class the properly parse the command line.