Add note and delete note feature

[josepholim]

• Implemented features for adding note and deleting note, with the test cases.
• Adapt the User Guide for notes to add and delete note by id.

[codecov]

Codecov Report

Merging #39 (4abc955) into master (0c0fde5) will decrease coverage by 0.38%.
The diff coverage is 54.45%.

@@             Coverage Diff              @@
##             master      #39      +/-   ##
============================================
- Coverage     74.79%   74.42%   -0.38%     
- Complexity      492      516      +24     
============================================
  Files            91       97       +6     
  Lines          1615     1701      +86     
  Branches        155      163       +8     
============================================
+ Hits           1208     1266      +58     
- Misses          360      384      +24     
- Partials         47       51       +4     

Files	Coverage Δ
...a/seedu/address/logic/commands/AddNoteCommand.java	100.00% <100.00%> (ø)
...eedu/address/logic/commands/DeleteNoteCommand.java	100.00% <100.00%> (ø)
...ain/java/seedu/address/logic/parser/CliSyntax.java	93.75% <100.00%> (+1.44%)	⬆️
...ain/java/seedu/address/model/note/NoteContent.java	100.00% <100.00%> (ø)
.../main/java/seedu/address/model/note/NoteTitle.java	100.00% <100.00%> (ø)
...a/seedu/address/logic/parser/AddCommandParser.java	75.00% <0.00%> (-25.00%)	⬇️
...eedu/address/logic/parser/DeleteCommandParser.java	75.00% <0.00%> (-25.00%)	⬇️
...c/main/java/seedu/address/model/person/Person.java	94.64% <90.90%> (-1.28%)	⬇️
.../java/seedu/address/model/util/SampleDataUtil.java	13.04% <0.00%> (ø)
...in/java/seedu/address/storage/JsonAdaptedNote.java	69.23% <80.00%> (+69.23%)	⬆️
... and 4 more

... and 1 file with indirect coverage changes

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[AndrewJanong]

Looks good! Just add more test cases later.