Normalize enum variant names

[rkr35]

Closes #9 .

Strips prefixes from enum variants and normalizes the case to PascalCase.

Enum variants that become invalid Rust identifiers after stripping will retain their prefixes, but the case of the variant still gets normalized to PascalCase.

Examples of generated enums

All the variants no longer have a common prefix:

#[repr(u8)]
pub enum ECsgOper {
    Active,
    Add,
    Subtract,
    Intersect,
    Deintersect,
    Max,
}

A variant named Self after stripping still retains its prefix:

#[repr(u8)]
pub enum EBehaviorContext {
    BcontextSelf, // Compiler error if variant was simply called `Self`
    MyInstigator,
    OtherEventParticipant,
    EventData,
    UseContextObject,
    Max,
}

A variant that begins with a number after stripping still retains its prefix:

#[repr(u8)]
pub enum ESliderType {
    St1d, // This and the following variant would not compile if they were called "1d" and "2d" respectively.
    St2d,
    Max,
}

A variant that becomes an empty string after stripping still retains its prefix:

#[repr(u8)]
pub enum EBehaviorCounterID {
    Bcounter, // The prefix is "Bcounter", but removing that prefix leaves an empty string.
    Bcounter1, // Incidentally, another example of retaining the prefix because the stripped version begins with a number.
    Max,
}