Been meaning to do this port for a while and since it makes passing
around file handles (presumably alongside the in mem obj form) a lot
simpler/nicer and the implementations of all the config file handling
much more terse with less presumptions about the form of filename/dir
`str` values all over the place B)
moar technically, let's us:
- drop remaining `.config` usage of `os.path`.
- return `Path`s from most routines.
- adds a special case to `get_conf_path()` such that if the input name
contains a `pps.` pattern, we avoid validating the name; this is going
to be used by new `.accounting.open_pps()` code which will instead
write a separate TOML file for each account B)
7b3d724908