DG: Add Tags feature

[Silvernitro]

• Update Model component to include UniqueTagMap (includes updated diagram)
• Add Tags feature
  • Explain our implementation of tags
  • What happens when a module is added (includes diagram)
  • What happens when module is deleted (includes diagram)
  • Editing a module

View here: https://silvernitro.github.io/tp/DeveloperGuide.html#tags-feature

Closes #183 & #186

[codecov-io]

Codecov Report

Merging #192 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #192   +/-   ##
=========================================
  Coverage     75.67%   75.67%           
  Complexity      586      586           
=========================================
  Files            96       96           
  Lines          1768     1768           
  Branches        183      183           
=========================================
  Hits           1338     1338           
  Misses          345      345           
  Partials         85       85           

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[yan-soon]

LGTM!!!!!!

[Silvernitro]

Update: Change the Module --> Tag association from composition to navigability as discussed. Yes I made a typo in the commit LOL so I hope this clears confusion