Parsers for naming conventions of earth observation products and datasets

```rust use eoidentifiers::Identifier; use eoidentifiers::identifiers::sentinel2::ProductLevel; use std::str::FromStr; use chrono::{NaiveDate, NaiveDateTime, NaiveTime};

fn example() { let ident = Identifier::fromstr("S2AMSIL1C20170105T013442N0204R031T53NMJ_20170105T013443") .unwrap();

if let Identifier::Sentinel2Product(product) = ident {
    assert_eq!(product.product_level, ProductLevel::L1C);
    assert_eq!(
        product.start_datetime,
        NaiveDateTime::new(NaiveDate::from_ymd(2017, 1, 5), NaiveTime::from_hms(1, 34, 42))
    );
    assert_eq!(product.relative_orbit_number, 31);
}
else {
    unreachable!();
}

} ```

This crate is at an early stage. There are lots of parser missing - pull requests are welcome.