A lot of campaigns want to define custom factions. This allows them to
do so without us having to fill the built-in factions list with a bunch
of campaign-specific factions. It also makes custom campaigns more
portable as they don't need to also distribute the custom faction files.
Comments! No more failures because you accidentally used a trailing
comma!
JSON still supported since it's basically free, but we should probably
remove that in 8 just so the docs can be less confusing for users who
will be confused if only one format is documented (and we definitely
won't maintain duplicate docs).
Eager loading meant that users would need to restart Liberation to pick
up changes to faction files. That's annoying for modders, slows down
start up, and uselessly sits in RAM when it's not needed after game
creation.
Also removes the __getitem__ and __iter__ methods in favor of named
methods, since the dunder methods are more or less impenetrable for IDEs
and grep.
