mods: Move mod content related logic to dedicated package (#829)

Moves the `Mod` class and related logic to its own source files

Author: Alystrasz

primedev/Northstar.cmake

@@ -85,6 +85,8 @@ add_library(
     "mods/compiled/modkeyvalues.cpp"
     "mods/compiled/modpdef.cpp"
     "mods/compiled/modscriptsrson.cpp"
+    "mods/mod.cpp"
+    "mods/mod.h"
     "mods/modmanager.cpp"
     "mods/modmanager.h"
     "mods/modsavefiles.cpp"