Added "order" argument to drawing functions.

[jeromekelleher]

Add a new order argument to the various drawing functions that can be either tree (the natural order arising from the quintuply linked trees) or minlex, the ordering from @brianzhang01's minlex_postorder tree traversal functions.

Since this is much better, we've changed the default ordering, so that people's trees will look different now. The small chance of breakage seems worth it. As this is a breaking change, I've pinged a good few of you for review - feel free to just ignore this or "approve" if you're not bothered.

This ended up being a bit more involved than I had expected, but I think it's good now.

Closes #389

[codecov]

Codecov Report

Merging #566 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #566      +/-   ##
==========================================
+ Coverage   87.35%   87.36%   +0.01%     
==========================================
  Files          22       22              
  Lines       16682    16696      +14     
  Branches     3260     3262       +2     
==========================================
+ Hits        14573    14587      +14     
  Misses       1030     1030              
  Partials     1079     1079              

Flag	Coverage Δ
#c_tests	88.61% <100.00%> (+0.01%)	⬆️
#python_c_tests	90.44% <100.00%> (+0.01%)	⬆️
#python_tests	99.05% <100.00%> (+<0.01%)	⬆️

Impacted Files	Coverage Δ
python/tskit/trees.py	98.18% <ø> (ø)
python/tskit/drawing.py	99.82% <100.00%> (+<0.01%)	⬆️

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[petrelharp]

Sounds good!

[jeromekelleher]

This can wait until #555 is in.

[brianzhang01]

Only took a skim, but it looks good to me.

[hyanwong]

Yeah. LGTM too. I worried that I might need a minlex_preorder function for the new SVG drawing functionality, but it turns out not, and this change should slot in quite easily.

[jeromekelleher]

OK, great. Let's try to get the main SVG stuff in first and then I'll update this PR.

[hyanwong]

@jeromekelleher the main SVG stuff is ready to merge I think.

[benjeffery]

Great! Just a couple of typos in docstrings, and one code style suggestion that I'm not very attached to.

[jeromekelleher]

Great, thanks @benjeffery. I'll rebase this and fix conflicts when @hyanwong's merge queue has settled down, no point in making his life more difficult right now.

[benjeffery]

Talking to @hyanwong that he'd like this in first - are you happy for me to rebase and merge?

[jeromekelleher]

Sure, if you don't mind resolving the merge conflicts here. I think it's a mistake though, as it'll add a bunch more conflicts for @hyanwong to resolve in his series of PRs.