Added Data.Database.Load for multiple files

Doesn't throw if a file is missing, takes cache parameter
Added Serializable attributes
Added data caching
Renamed DatabaseWarningException
Converted keyword db to JSON
Fixed DatabaseCsv naming
Minor changes
Added MandatoryAttribute for JSON data
Converted motions to JSON
Converted chairs to JSON
Converted char cards to JSON
Converted pets to JSON
Converted items to JSON
Converted skills to JSON
Converted races to JSON
Follow up a313e6e0298a0ed4aaaa372bb133afabc82db60b

Exp and gold not mandatory
Follow up d94172396d381a5b687dec3e6ec6daf657e9f0cd

Race not mandatory
Removed skill_ranks.txt
Changed ancient drops db to use %

instead of a 0-1 float
Converted titles to JSON