Update DG user stories, use cases and manual testing sections and some test changes

[TanLeYang]

• Updated the above mentioned sections of the DG
• Some refinements to the tests for Name, Genre and Tag
• Add tests for ViewTypeManager

[codecov-io]

Codecov Report

Merging #170 into master will decrease coverage by 0.16%.
The diff coverage is 8.69%.

@@             Coverage Diff              @@
##             master     #170      +/-   ##
============================================
- Coverage     71.67%   71.51%   -0.17%     
- Complexity      746      749       +3     
============================================
  Files           127      127              
  Lines          2415     2426      +11     
  Branches        270      267       -3     
============================================
+ Hits           1731     1735       +4     
- Misses          584      593       +9     
+ Partials        100       98       -2     

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/seedu/bookmark/model/book/Genre.java	83.33% <ø> (ø)	7.00 <0.00> (ø)
src/main/java/seedu/bookmark/ui/BookCard.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
src/main/java/seedu/bookmark/ui/MainWindow.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ain/java/seedu/bookmark/logic/ViewTypeManager.java	100.00% <100.00%> (+21.42%)	8.00 <1.00> (+3.00)
.../main/java/seedu/bookmark/model/history/State.java	80.76% <100.00%> (ø)	12.00 <1.00> (ø)

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[pennhanlee]

LGTM besides a small typo in DG

[pennhanlee]

There is a typo with Test genre

[TanLeYang]

Oh right nice catch!

[pangpuncake]

LGTM!

[angrybunny123]

LGTM 👍

[mgiang2015]

LGTM!