src/*.h: Remember to include lua.h for lua_State definition
Add src/message.c containing catalog related functions. Add :get_catalog as method on id128 objects
src/journal.lua: Add :get_catalog method; written in lua
src/journal.c: return a boolean from `next` and `previous`
src/*.lua: Call error with a level
src/message.lua: Add module that has a list of common message ids