Adjust command-line arguments to use '-' consistently instead of no spaces or camelCase

Issue/feature addressed

This MR adjusts command-line arguments to use '-' consistently instead of no spaces or camelCase.

Proposed solution

This is done in a manner that enables the new command line arguments, e.g. --forceoutput becomes --force-output, but prints a warning that the command line argument is deprecated (that could be turned into an error in future releases).

Implementation

Since we use boost::program_options, the general idea is to define a map of deprecated options, e.g.

// Deprecated options: introduced in 5.4.0 to homogenise command-line
// options to use '-' instead of camelCase or no spaces.
std::map<std::string, std::string> deprecated = {
    {"forceoutput", "force-output"},
    {"noequispaced", "no-equispaced"},
    {"useSessionVariables", "use-session-variables"},
    {"useSessionExpansion", "use-session-expansion"}
};

which populates options in the po::options_description object

po::options_description dep;
for (auto &d : deprecated)
{
    std::string description = "Deprecated: use --" + d.second;
    dep.add_options()(d.first.c_str(), description.c_str());
}

After parsing we set the new options in the po::variables_map object:

// Deal with deprecated options.
for (auto &d : deprecated)
{
    if (vm.count(d.first))
    {
        std::cerr << "WARNING: --" << d.first << " deprecated: use --"
                  << d.second << std::endl;
        vm.emplace(d.second, po::variable_value(vm[d.first]));
    }
}

Tests

Code and tests have been adjusted to use the new options.

Suggested reviewers

@ccantwel @CFD-Xing

Notes

Please add any other information that could be useful for reviewers.

Checklist

• Functions and classes, or changes to them, are documented.
• User guide/documentation is updated.
• Changelog is updated.
• Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).