fix some things, adjust GUI elements

- messages are now actually sent (bug in parse player list)
- no more crashes on sending mail (forgot to make variables local)
- actually handle CC and BCC fields instead of leaving them empty, duh
- make new functions be under the mail namespace
- add util functions to ensure the new format, parse and player list as well as checking whether a player is in that list or not
- rearrange some GUI elements (tighter spacing, grouping, increase window height to be consistent)
- convert mails to new format only as needed (old mails stay intact in case someone reverts to old version)
- mails are shaded differently in inbox, depending on whether the player is in the TO field
- FROM, TO and CC fields are all displayed when reading a mail
- add "Reply All" button (TO includes all original recipients plus the sender, but excluding the player himself, while adopting the CC field. To contrast: "Reply" just sets the original sender as TO and leaves the rest empty)
- move reply, replyall and forward to their own functions in GUI (was duplicated for inbox and show mail)
- don't needlessly set messages table when we do nothing but go back

api.lua

@@ -28,6 +28,9 @@ function mail.send(src, dst, subject, body)
 		m.body = body
 	end
 
+	local cc
+	local bcc
+	local extra
 	-- log mail send action
 	if m.cc or m.bcc then
 		if m.cc then
@@ -43,22 +46,22 @@ function mail.send(src, dst, subject, body)
 		else
 			bcc = ""
 		end
-		extra = "(" .. cc .. bcc .. ") "
+		extra = " (" .. cc .. bcc .. ")"
 	else
 		extra = ""
 	end
-	minetest.log("action", "[mail] '" .. m.from .. "' sends mail to '" .. m.to ..
+	minetest.log("action", "[mail] '" .. m.from .. "' sends mail to '" .. m.to .. "'" ..
 		extra .. "' with subject '" .. m.subject .. "' and body: '" .. m.body .. "'")
 
 
 	-- normalize to, cc and bcc while compiling a list of all recipients
 	local recipients = {}
-	m.to = normalize_players_and_add_recipients(m.to, recipients)
+	m.to = mail.normalize_players_and_add_recipients(m.to, recipients)
 	if m.cc then
-		m.cc = normalize_players_and_add_recipients(m.cc, recipients)
+		m.cc = mail.normalize_players_and_add_recipients(m.cc, recipients)
 	end
 	if m.bcc then
-		m.bcc = normalize_players_and_add_recipients(m.bcc, recipients)
+		m.bcc = mail.normalize_players_and_add_recipients(m.bcc, recipients)
 	end
 
 	-- form the actual mail