Added base lua manager

- CMakeLists.txt, Makefile, and appveyor now use luajit
- lua/LuaManager.[ch]pp has been added which includes a basic script loader & thread scheduler
- SCRIPTSDIR has been added to settings.[ch]pp, this specifies what directory lua scripts should be loaded from
- Makefile has been updated to include lua/LuaManager.[ch]pp

scripts/test.lua

@@ -0,0 +1,3 @@
+print("Hello world!")
+wait(2)
+print("Hello world ~2 seconds later!")