Fix Functionality bugs

[btbrandon]

Key Changes:

• Refactor EditCommand to ensure that a command consisting of "m/" and any other prefix will throw an error message
• Refactor Edit Command section in UG to document usage of edit command more clearly and specify which keywords are not supported for the respective command formats
• Add test case in EditCommandParserTest to support the changes
• Refactor MESSAGE_USAGE of Add, Delete, Edit, Find, Grade and Module commands for user-friendliness and standardisation
• Fix bug in Filter Command section of UG where fullstop is inside quotation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ	Complexity Δ
.../java/seedu/address/logic/commands/AddCommand.java	100.00% <100.00%> (ø)	8.00 <1.00> (ø)
...va/seedu/address/logic/commands/DeleteCommand.java	91.66% <100.00%> (+0.14%)	20.00 <1.00> (+1.00)
...java/seedu/address/logic/commands/EditCommand.java	93.43% <100.00%> (ø)	20.00 <0.00> (ø)
...java/seedu/address/logic/commands/FindCommand.java	100.00% <ø> (ø)	9.00 <0.00> (ø)
...ava/seedu/address/logic/commands/GradeCommand.java	100.00% <100.00%> (ø)	12.00 <1.00> (ø)
...va/seedu/address/logic/commands/ModuleCommand.java	100.00% <100.00%> (ø)	12.00 <1.00> (ø)
.../seedu/address/logic/parser/EditCommandParser.java	100.00% <100.00%> (ø)	17.00 <0.00> (+6.00)
...c/main/java/seedu/address/model/person/Module.java	94.44% <ø> (ø)	11.00 <0.00> (ø)

[ethan-goh]

LGTM