Add clear subcommand

[chrissimpkins]

to remove all metadata beyond Version [\d.]+ and start from scratch.

[chrissimpkins]

Adding this in the new libfv library that will be part of this package. New subcommand in the font-v executable will follow the release of the library

[chrissimpkins]

This functionality has been added to the libfv library. Will add subcommand to font-v following the release of the libfv library.