Add a types module to help refactor type checking

Type checking will be performed in unit tests, but will be an
empty function at runtime.

src/lua/types.lua

@@ -44,4 +44,8 @@ function types.matches_pattern(pattern)
 	end
 end
 
+function types.check(...)
+
+end
+
 return types

src/lua/util.lua

@@ -1,14 +1,14 @@
 
 local sql = require("lsqlite3")
 local config = require("config")
+local types = require("types")
 local util = {}
 
 --[[
 Runs an sql query and receives the 3 arguments back, prints a nice error
 message on fail, and returns true on success.
 ]]
-function util.sqlassert(...)
-	local r,errcode,err = ...
+function util.sqlassert(r, errcode, err)
 	if not r then
 		error(string.format("%d: %s",errcode, err))
 	end