Moved list of mods logic to a new CModManager class.
The list of enabled mods is now managed by a flag instead of directory
names of mods.
Mods are now disabled by default.
Also general cleanup, fixing issues from the code review in
https://github.com/colobot/colobot/pull/1191 and fixing linter issues.
Regression: the state of enabled/disabled mods is now not persistent.
The plan is to use some kind of config file for this.
MrSimbax