Use `directories` crate to find and install fonts for CLI

[Xiphoseer]

Use https://docs.rs/directories to specify and use well-known directories to search for CHSETS and also provide features to list and install them there.

• ProjectDirs::from("eu.dseiler.sdo", "Xiphoseer", "SDO-Tool") (default, tool specific)
• BaseDirs::data_dir + "signum" (more risk of conflict, would be usable by other tools)
• UserDirs::font_dir + "Signum" (type oriented, mac and linux only)