MakeAverageDataset pipeline prepared for v4.0.0 release

Main Script: Supplemental/MakeAverageDataset/MakeAverageDataset.sh

1. Made sure it has a usage function that uses cat <<EOF
   a. Although several of the parameter descriptions are still TBW
2. Have a get_options function that uses global variable names that are similar to the ones that are used in the main function yet are clearly recognizable as those set by the get_options function (names start with p_ for parameter)
3. main function gets its parameters positionally
4. main function uses local variables instead of global variables from the get_options function
5. All communication with the user (informational, debugging, or error messages) are via calls to log_* functions defined in a shared standard library of bash functions
6. Verification of the necessary environment variables is done "first thing" in the "global" (non-function) part of the script.
7. The global (non-function) part of the script checks for the use of positional or named parameters on the command line and only uses the get_options function if named parameters are used. This (along with some of the other changes above) allows invocation of the script using positional parameters or named parameters.