Modify `find` Command to Accept Prefixes

[RobotWizzard]

Resolves #175

Issues to consider:

• The current implementation allows for searching through each client's rental information list only through the k/ prefix.
• It is not user-friendly to allow find to search through rental information without showing the results through the UI.
• Should a new rfind command be added?
• Should the rental information list UI be decoupled from a single client?

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 97.61905% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../seedu/address/logic/parser/FindCommandParser.java	95.83%	0 Missing and 1 partial :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...java/seedu/address/logic/commands/FindCommand.java	90.00% <100.00%> (+2.00%)	8.00 <1.00> (+1.00)
src/main/java/seedu/address/model/client/Name.java	92.85% <ø> (ø)	6.00 <0.00> (ø)
...dress/model/tag/TagsContainsKeywordsPredicate.java	100.00% <100.00%> (ø)	7.00 <7.00> (?)
.../seedu/address/logic/parser/FindCommandParser.java	90.32% <95.83%> (+1.43%)	11.00 <9.00> (+4.00)

... and 5 files with indirect coverage changes