Extend the use of recent history

Partly a follow-up to !69 (merged), !83 (merged) and !89 (merged).

• Move recent history management to mousepad_util.c (already discussed in !89 (comment 30188))
• Use history encoding in the "Open" dialog
• Use history encoding in the encoding dialog
• Always use history encoding when opening a file
• Store also the user set language in the recent history
• Store also the cursor position in the recent history