Add a casing style parameter to AccessorFunc()

[TomDotBat]

This adds a new parameter to AccessorFunc which makes it possible to change the casing style by passing a CASING_ enum. The casing styles I have added are:

• PascalCase
• camelCase
• snake_case
• UPPER_SNAKE_CASE

This will be extremely helpful to people who don't want to use PascalCase on their table methods. To ensure compatibility isn't broken, PascalCase will be the default option when the casing parameter isn't populated.

[garryspins]

All mah homies love UPPER_SNAKE_CASE

[TobyDHKing]

ButPascalCase IsReallyEpic

[GitSparTV]

Gmod uses this function for its own styling

[thekillertoaster]

PascalCase is the way to go