Retain a stringbuilder to mutate the string rather than finalizing temporary strings
yields some speed improvements (less gen0 string objects allocated)
GCI, DSV, DUC are already supported, so I've written the abstraction for those and seed the Handler list on startup.
Can add a new class with recognition via SaveUtil.Handlers.Add(myHandler);
Remove some unnecessary properties from SaveFile
Enumerate checksum flag results for GC memcard checking
Remove unnecessary checks on savefile type
Add some documentation
Decapitalize some method parameters
be explicit that the string is empty rather than possibly missing
disallow encrypted export for BK4 (they're not encrypted), removes type
check
simplify replaceall in showdownset (don't call ReplaceAll 4x, just get
valid chars and rebuild)
simplify get ribbon sprite name (precompute ToLower and appended values
