Allow mixed case for anagram puzzles

[NoxHarmonium]

It might not be the cleanest solution but is probably the best workaround we have until https://github.com/AustralianSynchrotron/openday-scavenger/issues/118 is done

It words because the server expects the correct answer to be in the form element "answer" but it doesn't care what type of input the "answer" form element is, so we can make the "answer" form element hidden and put whatever we want in there programmatically.

I think we do this elsewhere for more complex puzzles anyway.

[NoxHarmonium]

Fixed merge conflict

[luigiferiani]

Thank you very much, this makes a lot of sense :)