Modify existing delete command to "cdelete"

[RobotWizzard]

Change the delete client command to cdelete.

Fixes #104

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Files with missing lines	Coverage Δ	Complexity Δ
...du/address/logic/commands/DeleteClientCommand.java	100.00% <100.00%> (ø)	7.00 <1.00> (?)
.../seedu/address/logic/parser/AddressBookParser.java	78.26% <100.00%> (ø)	11.00 <0.00> (ø)
...ddress/logic/parser/DeleteClientCommandParser.java	100.00% <100.00%> (ø)	2.00 <1.00> (?)

[zackjh]

LGTM!