Replaced campaign bonuses from using 3 integers to store anything with
type-safe version that uses std::variant that ensures that all bonuses
are in correct state.
Also removed "interesting" solutions like storing primary skills using
bit shifts.
Prerequirement for HotA campaign support
- files now generally contain only 1 class (except for tightly coupled
classes)
- files are now located in lib/entities/artifact directory
- removed excessive includes
No changes to functionality
Ivan Savenko
Laserlicht