merge identical genre tags in album info

[davebiffuk]

This PR merges duplicate track genre tags when constructing the album genre info. This change will help players which display the album genre to avoid cluttering their display with a repeated list of identical genre names. This idea came from https://github.com/peguerosdc/subplayer/issues/48

[codecov[bot]]

Codecov Report

Merging #221 (a1eeeb8) into master (e6e20d1) will not change coverage. The diff coverage is 100.00%.

:exclamation: Current head a1eeeb8 differs from pull request most recent head e8d3f16. Consider uploading reports for the commit e8d3f16 to get more accurate results

@@           Coverage Diff           @@
##           master     #221   +/-   ##
=======================================
  Coverage   86.67%   86.67%           
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  Files          40       40           
  Lines        3684     3684           
=======================================
  Hits         3193     3193           
  Misses        491      491           

Impacted Files	Coverage Δ
supysonic/db.py	93.75% <100.00%> (ø)

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[spl0k]

Hi, thank you for the PR.

I guess I didn't understand Pony's attribute lifting properly, it seems to have some confusing behaviour. I'll run some tests on this, there might be a better way to fix it.

[davebiffuk]

I know nothing about Pony, sorry, so this is a naive patch but it works for me. If there's a better way, that's great.

[davebiffuk]

Nice, thanks!