Update Client Add and Find Function

[winstonlimjy]

Changes:

• Allow client to have same name. Fixes #135
• Check for duplicate with all 3 fields: name + phone + email
• Finding of rental information, all fields. Fixes #136
• Allow finding of substrings. Fixes #149
• Create a new contains method in StringUtil.java
• Create test cases for finding rental information. Fixes #150
• Display no rental information when find function found nothing. Fixes #148

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 81.48148% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...nt/RentalInformationContainsKeywordsPredicate.java	84.84%	2 Missing and 3 partials :warning:
...c/main/java/seedu/address/model/client/Client.java	25.00%	0 Missing and 3 partials :warning:
...java/seedu/address/logic/commands/FindCommand.java	66.66%	0 Missing and 2 partials :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...in/java/seedu/address/commons/util/StringUtil.java	95.83% <100.00%> (+1.09%)	8.00 <1.00> (+1.00)
...seedu/address/logic/commands/AddClientCommand.java	100.00% <ø> (ø)	8.00 <0.00> (ø)
.../seedu/address/logic/parser/FindCommandParser.java	77.77% <ø> (ø)	6.00 <0.00> (ø)
...rc/main/java/seedu/address/model/ModelManager.java	93.65% <100.00%> (+0.31%)	28.00 <0.00> (+1.00)
...rc/main/java/seedu/address/model/client/Email.java	90.00% <ø> (ø)	11.00 <0.00> (ø)
...s/model/client/EmailContainsKeywordsPredicate.java	77.77% <100.00%> (+16.66%)	8.00 <1.00> (+2.00)
...ss/model/client/NameContainsKeywordsPredicate.java	88.88% <100.00%> (ø)	9.00 <1.00> (ø)
...rc/main/java/seedu/address/model/client/Phone.java	90.00% <ø> (ø)	11.00 <0.00> (ø)
...s/model/client/PhoneContainsKeywordsPredicate.java	77.77% <100.00%> (+16.66%)	8.00 <1.00> (+2.00)
...java/seedu/address/logic/commands/FindCommand.java	88.00% <66.66%> (-2.91%)	7.00 <1.00> (ø)
... and 2 more