Add tutor function

[ruishanteo]

• Refactor person model
• Remove address
• Remove tags
• Add add tutor command
• Edit edit person command (for updated person model)

[codecov]

Codecov Report

Merging #61 (5cee758) into refactor-person-as-tutor (f9831d0) will decrease coverage by 1.12%.
The diff coverage is 96.42%.

@@                      Coverage Diff                       @@
##             refactor-person-as-tutor      #61      +/-   ##
==============================================================
- Coverage                       75.26%   74.15%   -1.12%     
+ Complexity                        419      400      -19     
==============================================================
  Files                              71       70       -1     
  Lines                            1338     1265      -73     
  Branches                          126      114      -12     
==============================================================
- Hits                             1007      938      -69     
+ Misses                            301      298       -3     
+ Partials                           30       29       -1     

Files	Coverage Δ
src/main/java/seedu/address/logic/Messages.java	83.33% <100.00%> (-4.17%)	⬇️
.../seedu/address/logic/commands/AddTutorCommand.java	100.00% <100.00%> (ø)
...java/seedu/address/logic/commands/EditCommand.java	96.87% <100.00%> (-0.57%)	⬇️
...du/address/logic/parser/AddTutorCommandParser.java	100.00% <100.00%> (ø)
.../seedu/address/logic/parser/AddressBookParser.java	100.00% <100.00%> (ø)
.../seedu/address/logic/parser/EditCommandParser.java	75.00% <100.00%> (-17.60%)	⬇️
.../java/seedu/address/model/util/SampleDataUtil.java	0.00% <ø> (-20.00%)	⬇️
.../java/seedu/address/storage/JsonAdaptedPerson.java	100.00% <100.00%> (ø)
src/main/java/seedu/address/ui/PersonCard.java	0.00% <ø> (ø)
...c/main/java/seedu/address/model/person/Person.java	96.29% <75.00%> (-0.93%)	⬇️

... and 2 files with indirect coverage changes

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[mfjkri]

Thanks Rui Shan. LGTM!

@Jweng88 Please use this branch for list and edit command (your PRs should merge back to this branch instead of master).

We will ensure coverage report is acceptable before merging this branch back to master.