Support and tests for GPX waypoint accuracy information/values.

[caspervg]

No description provided.

[frewsxcv]

thanks for the pr! will wait to see if @brendanashworth has some thoughts about this change, otherwise i can take a look sometime

[brendanashworth]

Thanks for the PR, this looks really nice! Just a question about using an enum.

[brendanashworth]

What do you think about using an enum here? This way users wouldn't need to validate results because we'd already have validated them.

We could probably add a fix.rs and use it like fix::consume(reader) or something, thoughts?

[caspervg]

@brendanashworth Thanks for the enum suggestion. I've updated it as you suggested. I wasn't sure how to handle values that are not within the spec. For now they are wrapped inside a Fix::Other(string_value) enum value, but perhaps it should instead return an error.

I would personally prefer the current solution from a practical point of view (I'm unfortunately dealing with data that has unsupported values in the <fix> tags), but I'm fine with either way.

[brendanashworth]

@caspervg that looks really nice, I appreciate the work you did on this. If we're dealing with data that isn't spec-compliant that seems like a logical way to handle it, good call.

I've merged this as 13ca700 after some nit fies, thank you very much!