Progress: url paths

Progress: url paths

In particular, begin initial work on output formats other than HTML.
- This is initial work and is subject to change (currently a brainstorm).

Add more common paths and appropriate files and classes.
- Most of these classes are stubs and will be populated eventually.

Cleanup the c_base_html class.

Move pr_process_arguments() to c_standard_path where it resides alongside the $arguments class variable.

Be more verbose with the function name pr_paths_create() (now called pr_paths_create_always()).

Add additional columns to the file database table.