Index lifecycle docs

[jeromekelleher]

Depends on #709 - diff will be easier to read when it's merged.

[codecov]

Codecov Report

Merging #713 into master will increase coverage by 2.30%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #713      +/-   ##
==========================================
+ Coverage   85.43%   87.74%   +2.30%     
==========================================
  Files           8       24      +16     
  Lines        9615    19109    +9494     
  Branches     1837     3563    +1726     
==========================================
+ Hits         8215    16768    +8553     
- Misses        799     1273     +474     
- Partials      601     1068     +467     

Flag	Coverage Δ
#c_tests	85.44% <100.00%> (+<0.01%)	⬆️
#python_c_tests	90.08% <ø> (?)
#python_tests	99.00% <ø> (?)

Impacted Files	Coverage Δ
c/tskit/tables.c	81.39% <100.00%> (+0.01%)	⬆️
c/tskit/core.h	100.00% <0.00%> (ø)
python/tskit/formats.py	100.00% <0.00%> (ø)
python/tskit/trees.py	98.24% <0.00%> (ø)
python/tskit/tables.py	99.68% <0.00%> (ø)
python/tskit/exceptions.py	100.00% <0.00%> (ø)
python/tskit/__init__.py	100.00% <0.00%> (ø)
python/tskit/__main__.py	0.00% <0.00%> (ø)
python/tskit/vcf.py	100.00% <0.00%> (ø)
python/tskit/_version.py	100.00% <0.00%> (ø)
... and 8 more

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[jeromekelleher]

This is a fairly straightforward improvement, so I'm going to merge.