This method did not do any checks for validity of its parameters and its
behavior wasn't consistent in that it woldn't set specified config in
case `Feature` was already enabled. Now it will.
I shamefully ended up doing another mega-commit, because a lot of things
needed to be redone at once and it was easier that way on me. No one
really consistently tracks what I'm doing with these commits anyway.
This adds a whole bunch of code to deal with proper clean up for Acedia,
so it doesn't crash on map change and also replaces old event/listener
system with new signals/slots one.
We cannot rely on `Feature`'s static constructor to be called for every
feature class, so we move out relevant code into separate
`LoadConfigs()` method.
This patch changes how `Feature`s configs work - they are now required
to use a separate config object (each `Feature` their own class, derived
from `FeatureConfig`) that is to be used as a `perconfigobject` storage.
`Feature`s themselves are not supposed to interact with their config
objects directly, instead using JSON-serializable type, which should
allow us a universal way to change `Feature`'s config variables during
execution.
Anton Tarasenko