Decouple blacklist command from find command

[Dinoman44]

Fixes #163

[codecov[bot]]

Codecov Report

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

Files with missing lines	Coverage Δ	Complexity Δ
...u/address/logic/commands/BlacklistListCommand.java	100.00% <100.00%> (+33.33%)	2.00 <0.00> (ø)
...u/address/logic/commands/WhitelistListCommand.java	100.00% <100.00%> (ø)	2.00 <0.00> (ø)
.../seedu/address/model/person/ArgumentPredicate.java	82.69% <100.00%> (+0.69%)	22.00 <0.00> (ø)
.../address/model/person/ArgumentPredicateToFail.java	79.59% <100.00%> (-1.89%)	22.00 <0.00> (-2.00)

... and 1 file with indirect coverage changes