Added support for Floats

[nethunters-dev]

Added support for float type, uses ordered-float crate for float Eq and Hash.

[marmeladema]

Thank you for your contribution! I'll take a look next week :-)

[nethunters-dev]

You're welcome.

A quick heads up; it currently uses f64::from_str to parse the float from strings. Looking at the documentation for WireShark filters I couldn't find any mention of it supporting floating point numbers in forms other than decimal. The lexical crate (with the radix feature) has the ability to parse floats with a custom radix.