59 implement parser for role tag

[shardhrv]

For #59

Changelog:

• [x] Add parseRoles to ParseUtil to handle multiple roles being assigned to a single person
• [x] Add role tag to Person
• [x] Enable parsing for r/... commands for AddCommand, EditCommand
• [x] Update newly added role tags to storage
• [x] Add test cases for new classes and methods

Description:

Fully implemented role feature for each person. You are now able to add one of four roles (sponsor, attendee, vendor, volunteer) to each person. This role will also be displayed on the person card in green.

Relevant Screenshots:

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 71.60494% with 23 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../java/seedu/address/model/util/SampleDataUtil.java	30.00%	14 Missing :warning:
.../seedu/address/logic/parser/EditCommandParser.java	33.33%	2 Missing and 2 partials :warning:
src/main/java/seedu/address/ui/PersonCard.java	0.00%	3 Missing :warning:
...c/main/java/seedu/address/model/person/Person.java	71.42%	0 Missing and 2 partials :warning:

Files with missing lines	Coverage Δ	Complexity Δ
src/main/java/seedu/address/logic/Messages.java	86.36% <100.00%> (+1.36%)	3.00 <0.00> (ø)
.../java/seedu/address/logic/commands/AddCommand.java	100.00% <ø> (ø)	8.00 <0.00> (ø)
...java/seedu/address/logic/commands/EditCommand.java	96.73% <100.00%> (+0.22%)	13.00 <0.00> (ø)
...a/seedu/address/logic/parser/AddCommandParser.java	100.00% <100.00%> (ø)	5.00 <0.00> (ø)
...in/java/seedu/address/logic/parser/ParserUtil.java	91.07% <100.00%> (+1.07%)	20.00 <2.00> (+2.00)
src/main/java/seedu/address/model/role/Role.java	100.00% <100.00%> (ø)	14.00 <1.00> (+1.00)
...ain/java/seedu/address/model/role/RoleHandler.java	100.00% <100.00%> (ø)	10.00 <5.00> (ø)
.../java/seedu/address/storage/JsonAdaptedPerson.java	100.00% <100.00%> (ø)	12.00 <0.00> (+1.00)
...in/java/seedu/address/storage/JsonAdaptedRole.java	100.00% <100.00%> (ø)	4.00 <4.00> (?)
...c/main/java/seedu/address/model/person/Person.java	95.65% <71.42%> (-1.91%)	24.00 <1.00> (+1.00)	:arrow_down:
... and 3 more