Fix bugs

[plosslaw]

• Show each role requirement on a new line (Resolves [PE-D] Consider adding new line for each role #154)
• Throws parser exception: Unexpected argument for command "[command name]": [argument passed] when argument is
  passed to non-argument commands (Resolves [PE-D] Worker-list command #179)
• Add maximum of 50 workers per role to role requirement (Resolves [PE-D] shift-edit/shift-add: Assertion Error should return an error message instead #184)
• Throw duplicate roles detected error for shift-add and shift-edit (Resolves [PE-D] Adding the same role twice in shift-edit command error. #165)
• Change worker phone number to accept only Singapore phone numbers (8 digits, starting with 6, 8 or 9) (Resolves [PE-D] Phone number shld be valid phone number #176)
• Change AssignCommand to detect and throw error when duplicate workers is being assigned (Resolves Assign command does not detect duplicate workers being assigned to different roles #202, resolves mass assign: show error for duplicate worker in single call #203)
• Update UG for non-argument commands (Resolves UG: add information how extra parameters will be parsed #188)

[codecov-io]

Codecov Report

Merging #204 into master will decrease coverage by 0.02%.
The diff coverage is 65.51%.

@@             Coverage Diff              @@
##             master     #204      +/-   ##
============================================
- Coverage     67.59%   67.56%   -0.03%     
- Complexity      859      866       +7     
============================================
  Files           141      141              
  Lines          3135     3179      +44     
  Branches        434      442       +8     
============================================
+ Hits           2119     2148      +29     
- Misses          890      904      +14     
- Partials        126      127       +1     

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/mcscheduler/commons/core/Messages.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...heduler/logic/commands/WorkerAvailableCommand.java	27.45% <0.00%> (ø)	9.00 <0.00> (ø)
...a/mcscheduler/model/assignment/WorkerRolePair.java	76.00% <ø> (ø)	11.00 <0.00> (ø)
.../java/mcscheduler/model/shift/RoleRequirement.java	90.90% <ø> (ø)	21.00 <0.00> (ø)
src/main/java/mcscheduler/ui/ShiftCard.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
src/main/java/mcscheduler/ui/WorkerCard.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...main/java/mcscheduler/logic/parser/ParserUtil.java	59.23% <28.57%> (-3.63%)	26.00 <0.00> (ø)
...va/mcscheduler/logic/parser/McSchedulerParser.java	65.30% <100.00%> (+18.24%)	18.00 <0.00> (+6.00)
src/main/java/mcscheduler/model/worker/Phone.java	81.81% <100.00%> (+1.81%)	7.00 <1.00> (+1.00)
src/main/java/mcscheduler/model/worker/Worker.java	96.55% <100.00%> (ø)	27.00 <0.00> (ø)
... and 2 more

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[sigmund-c]

looks good!