Add support for GPX.jl

[alhirzel]

This is pending registration of GPX.jl and KMLTracks.jl and the merging of https://github.com/scls19fr/GPX.jl/pull/

[codecov]

Codecov Report

Merging #262 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #262   +/-   ##
=======================================
  Coverage   76.02%   76.02%           
=======================================
  Files           8        8           
  Lines         413      413           
=======================================
  Hits          314      314           
  Misses         99       99           

Impacted Files	Coverage Δ
src/registry.jl	92.64% <ø> (ø)

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[s-celles]

As mentioned in s-celles/KMLTracks.jl#6 (comment) maybe we should only focus on GPX.jl first (with both load and save and also with tests as mentioned in s-celles/GPX.jl#5 (comment)

[timholy]

Any magic bytes available? See my rant.

[alhirzel]

Hey @timholy, GPX is an XML-based format which does not have magic bytes in the traditional sense. The XML namespace is the closest thing. See example.

Perhaps there could be some content-aware file type detection mechanism which specializes for XML, but I feel it might end up being pretty fragile due to e.g. white space, file encoding, updated xmlns versions/URLs, etc. What are your thoughts? As @scls19fr mentioned we have a few more steps prior to taking this "prime time".

[timholy]

Sorry for the delay. I'm willing to merge this if you're still interested.

[alhirzel]

No problem Tim :) I haven't used this for a little while, but this should still be good to merge.

[timholy]

Thanks!

[timholy]

Oh, GPX was never registered! I'm reverting #299. Sorry.