#1672 (ok 4.5) MIME types should be lower case

[Olaf van der Spek]

MIME types are normally lower case but in PMA (MIME type and Browser display transformation) they're title case. That looks weird.

[Madhura Jayaratne]

Implemented with https://github.com/phpmyadmin/phpmyadmin/commit/2f8f1687fb6f7fe25bf5877818963b689c880535