Backend changes for loading and writing character data

Still as json, but loadPlayer now takes a character name
and reads it from disk and writePlayer now writes a player
to disk.
Whitespace/cleanup and server.py refactoring
Update XP button to increase XP by given amount
Serialization of prompt.json (the example and my main character)
Cleanup Loader.hs
Add regular items (which have names and counts)

Would like to add descriptions and move magical items
to a similar data structure internally.

Also changed item/power/feat/selected layout to be
striped tables.