Prevent invalid names from registering

For some reason the kore validators are broken.
It's nice to have proper error messages anyway I guess.

src/lua/init.lua

@@ -507,7 +507,7 @@ function claim(req)
 		--Get the page to claim a name
 		text = render(string.format("%s/_claim",domain),function()
 			print("cache miss, rendering claim page")
-			return pages.claim{}
+			return pages.claim{err=""}
 		end)
 	elseif method == "POST" then
 		--Actually claim a name
@@ -515,7 +515,7 @@ function claim(req)
 		local name = assert(http_argument_get_string(req,"user"))
 		--What in the world, Kore should be rejecting names that
 		--are not lower case & no symbols, but some still get through somehow.
-		if not name:match("^[a-z0-9]{1,30}$") then
+		if not name:match("^[a-z0-9]*$") then
 			print("Bad username:",name)
 			text = pages.claim{
 				err = "Usernames must match ^[a-z0-9]{1,30}$"