(1) First draft of the caching system for LuaAI. (2) Added validation
variables and setters/getters in the ai contexts, to allow LuaAI cache
check the movemaps for validity
...for strings, too
this is done by a) scanning for all .lua files additionally to all
.cfg files in FINDCFG and b) by adding the equivalent of a "commented
out" #textdomain DOMAIN declaration
next step: testing if it really does work as expected this should also
fix bug #15629 since the objectives are now *only* declared via some
lua magic
