Occlum SGX lib

Implementation for generate and verify SGX DCAP Quote for Occlum

Usage:

``` use occlum_sgx::SGXQuote;

fn main() -> Result<(), Box> { let quote: SGXQuote = [0u8; 64].try_into()?;

if quote.verify()? {
    println!("Quote is valid");
} else {
    println!("Quote is invalid");
}

let mrenclave = quote.mrenclave();
let mrsigner = quote.mrsigner();
let product_id = quote.product_id();
let version = quote.version();

println!("MrEnclave:\t{}", mrenclave);
println!("MrSigner:\t{}", mrsigner);
println!("ProdID:\t{}", product_id);
println!("Version:\t{}", version);

println!("\n{:#?}", quote);

Ok(())

} ```