Highscores improvements

Changes

Upgraded tibia.py required version to >=1.1 to use Highscore parsing.
get_highscores_tibiadata() renamed to get_highscores() and it now uses tibia.py parsing.
Old get_highscores function was removed.
Updated /highscores command to use new Highscores objects.
Updated scan_highscores task to use new get_highscores() function, and optimized it to use copy_records_to_table instead of 300 inserts.
Experience highscores are now saved in the database
Added experience related functions
Added global subcommand for /highscores, shows combined results from all (tracked) worlds.
Removed unused highscore related entries in config.
Highscores entries shown in /whois are now displayed in an embed field

/eval now shows output in a embed, showing the execution time
Fixed /versions, it wasn't working with packages that had . in them.
Fixed database migration to use UTC aware times.
Fixed DbDeath.exists function, it doesn't require killer anymore.
Added get_current_server_save_time() to find the datetime of the last server save (or the last server save before a specified date).