Add UTF-8 support and option to use case-insensitive attributes

[solenya]

Hello,
it would be great if UTF-8 support and option to use case-insensitive attributes were added.

Test case (UTF-8):
Group editor:
student = {
studentid:number, firstname:string, lastname:string, fieldofstudy:string
6, Lukas, Novotný, N-AplInf
}

Error: Expected "\n", "\r\n", "}", [-_a-z0-9.]i or delimiter but "ý" found.

[michaelrampl]

This is not due to missing UTF8 support but rather the parser only supports a custom set of characters supported. This change will require quite some effort as almost everything needs to be retested afterwards.