This can be used for "advanced" options which are for developers
to use for feature-flags and other configuration. Run time config
has some advantages over preprocessor defines:
* Can be changed without recompilation
* Sensitive to XDG_CONFIG_DIR, so flipping configs is easy
* Better compiler coverage (less conditionally compiled code means
less chance to break a different configuration). Also better
analysis coverage.
* Type safe config params
* Centralised documentation: it's in doxygen, in one place
No advanced config should be required by a general users. If a general
user does use one of these configs, it's probably because:
* There is a bug and one of these configs is a workaround
* A config in here is generally useful and should be moved into the
relevant application config and given UI.
For now, the config is read-only, and is read from the
"kicad_advanced" config file in the normal config dir.
John Beard