Fix PE-D Bugs

[MingYiAw]

Fix PE-D bugs related to edit command.

Closes #197
Closes #201
Closes #251

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ	Complexity Δ
src/main/java/seedu/address/logic/Messages.java	90.00% <ø> (ø)	3.00 <0.00> (ø)
...du/address/logic/commands/SearchPolicyCommand.java	96.15% <100.00%> (ø)	13.00 <0.00> (ø)
...in/java/seedu/address/logic/parser/ParserUtil.java	87.91% <100.00%> (ø)	24.00 <0.00> (ø)
...main/java/seedu/address/model/person/Birthday.java	94.11% <ø> (ø)	9.00 <0.00> (ø)

... and 9 files with indirect coverage changes

[The0nlyJuan]

LGTM