Branch resolve wrong error message

[gohqingkhang]

Resolves #298

Command to run:
addSubmissionStatus sm/A1 ss/Y

Original error message received:
Index is not a non-zero unsigned integer.

This error message is wrong as the error is not that the index given is a non-zero integer, but rather that the index was not given in the first place.

Corrected error message:

Invalid command format!
addSubmissionStatus: Adds a submission status to a student identified by index.
Parameters: [INDEX] sm/SUBMISSION_NAME ss/SUBMISSION_STATUS
Example: addSubmissionStatus 1 sm/Assignment 1 ss/Y

Similar error messages provided for addExamScore, addAttendance, addEcName and addEcNumber commands are amended as well.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ	Complexity Δ
...dress/logic/parser/AddAttendanceCommandParser.java	100.00% <100.00%> (ø)	6.00 <0.00> (+1.00)
...u/address/logic/parser/AddEcNameCommandParser.java	88.88% <100.00%> (-11.12%)	5.00 <0.00> (+1.00)	⬇️
...address/logic/parser/AddEcNumberCommandParser.java	85.71% <100.00%> (+2.38%)	4.00 <0.00> (+1.00)
...ddress/logic/parser/AddExamScoreCommandParser.java	100.00% <100.00%> (ø)	5.00 <0.00> (+1.00)
...logic/parser/AddSubmissionStatusCommandParser.java	100.00% <100.00%> (ø)	6.00 <0.00> (+1.00)

[BunnyHoppp]

LGTM