Simplify sorting and make it more readable (#58)

* Simplify sorting and make it more readable

* Make sorter local

* Fix sorters dropdowns go back to default

* Fix luacheck

* Move sorting dropdown values to selected_idxs

* Show previous sorters when going back from message/contacts/...

* Use shallow copy instead of original table

* Open mail interface with previous tab/dropdowns

* Rework mail.sort_messages

* Combine filter and sort, make filtering safe

* Remove checks and logging from sorters

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Co-authored-by: Athozus <athozus@gmail.com>

init.lua

@@ -21,7 +21,9 @@ mail = {
 		to = {},
 		cc = {},
 		bcc = {},
-		boxtab = {}
+		boxtab = {},
+		sortfield = {},
+		sortdirection = {}
 	},
 
 	message_drafts = {}