[MRG] minor updates to tax docs

[bluegenes]

• updates tax docs with query_md5 and query_filename column info
• genome fix: avoid printing query name for proper krona output

[codecov]

Codecov Report

Merging #1628 (d051d7a) into latest (d473199) will increase coverage by 7.63%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           latest    #1628      +/-   ##
==========================================
+ Coverage   81.81%   89.44%   +7.63%     
==========================================
  Files         110       83      -27     
  Lines       11171     7465    -3706     
  Branches     1371     1371              
==========================================
- Hits         9139     6677    -2462     
+ Misses       1792      548    -1244     
  Partials      240      240              

Flag	Coverage Δ
python	89.44% <50.00%> (ø)
rust	?

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Impacted Files	Coverage Δ
src/sourmash/tax/__main__.py	87.56% <50.00%> (ø)
src/core/src/index/storage.rs
src/core/src/signature.rs
src/core/src/index/search.rs
src/core/src/encodings.rs
src/core/src/lib.rs
src/core/src/sketch/minhash.rs
src/core/src/ffi/minhash.rs
src/core/src/index/mod.rs
src/core/src/sketch/hyperloglog/mod.rs
... and 18 more

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