Remove float value comparison

[marcelbuesing]

@killercup you were right previously, there is no need to compare floating point values. So besides obviously being more efficient it's also correct now, I ran into issues where the floating point comparison did not work. The reason why I removed the From implementation is basically that there is no way to access the signal_raw fn in the From implementation. Not super happy with how the generated code looks like so I am open to suggestions.

Additional changes:

• Update bitvec to 0.22
• bitvec 0.22 makes use of const generics and therefore requires min rust toolchain 1.51.0
• Use bitvec prelude import as types are either moved or at least no longer exposed under the root crate module.

[killercup]

Hey, sorry it took me a while to get to this! Thanks! :)