Delete GlotPress meta data on uninstall

[swissspidy]

Description

Fixes #71 by deleting meta data upon plugin uninstall.

How has this been tested? Successfully tested using wp plugin uninstall --skip-delete --deactivate traduttore.

Types of changes Extends uninstall routine to delete project and translation set meta data from GlotPress meta table.

Checklist:

• [x] My code is tested.
• [x] My code follows the WordPress code style.
• [x] My code has proper inline documentation.

[codecov-io]

Codecov Report

Merging #90 into master will increase coverage by 5.65%. The diff coverage is n/a.

@@             Coverage Diff              @@
##             master      #90      +/-   ##
============================================
+ Coverage     69.15%   74.81%   +5.65%     
+ Complexity      339      331       -8     
============================================
  Files            26       23       -3     
  Lines           830      798      -32     
============================================
+ Hits            574      597      +23     
+ Misses          256      201      -55

Impacted Files	Coverage Δ	Complexity Δ
inc/Project.php	96.22% <0%> (-3.78%)	40% <0%> (+4%)
inc/Repository/GitLab.php	96% <0%> (-0.3%)	11% <0%> (-1%)
inc/Repository/Bitbucket.php	97.61% <0%> (-0.11%)	24% <0%> (-1%)
inc/Repository/GitHub.php	100% <0%> (ø)	10% <0%> (-1%)	:arrow_down:
inc/WebhookHandler/Base.php	100% <0%> (ø)	10% <0%> (+9%)	:arrow_up:
inc/CLI/CacheCommand.php
inc/CLI/BuildCommand.php
inc/CLI/UpdateCommand.php
inc/WebhookHandler/GitLab.php	96.96% <0%> (+0.41%)	11% <0%> (ø)	:arrow_down:
inc/WebhookHandler/Bitbucket.php	91.89% <0%> (+0.98%)	12% <0%> (ø)	:arrow_down:
... and 1 more

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