add and edit commands involving distributors - distributors with same name or phone (unless it is 00000000) not allowed

[dyeosy98]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 466

• 52 of 151 (34.44%) changed or added relevant lines in 21 files are covered.
• 69 unchanged lines in 13 files lost coverage.
• Overall coverage decreased (-1.01%) to 29.238%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/main/java/seedu/address/MainApp.java	0	1	0.0%
src/main/java/seedu/address/logic/commands/AddDistributorCommand.java	2	4	50.0%
src/main/java/seedu/address/model/distributor/Distributor.java	16	18	88.89%
src/main/java/seedu/address/model/distributor/DistributorProduct.java	8	10	80.0%
src/main/java/seedu/address/logic/parser/AddDistributorCommandParser.java	0	3	0.0%
src/main/java/seedu/address/logic/parser/AllCommandsParser.java	0	4	0.0%
src/main/java/seedu/address/commons/events/ui/DistributorProductPanelSelectionChangedEvent.java	0	5	0.0%
src/main/java/seedu/address/logic/parser/AddCommandParser.java	0	5	0.0%
src/main/java/seedu/address/model/util/SampleDistributorsUtil.java	3	9	33.33%
src/main/java/seedu/address/logic/parser/ListDistributorProductsCommandParser.java	0	7	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/main/java/seedu/address/model/ModelManager.java	1	29.58%
src/main/java/seedu/address/logic/parser/AddCommandParser.java	1	0.0%
src/main/java/seedu/address/logic/parser/AddDistributorCommandParser.java	1	0.0%
src/main/java/seedu/address/model/tag/Tag.java	2	80.0%
src/main/java/seedu/address/model/distributor/UniqueDistributorList.java	2	69.77%
src/main/java/seedu/address/storage/XmlFileStorage.java	3	9.09%
src/main/java/seedu/address/model/DistributorBook.java	4	82.14%
src/main/java/seedu/address/storage/XmlAdaptedTag.java	6	0.0%
src/main/java/seedu/address/commons/util/XmlUtil.java	8	35.29%
src/main/java/seedu/address/storage/XmlSerializableDistributorBook.java	9	25.0%

Totals
Change from base Build 460:	-1.01%
Covered Lines:	1097
Relevant Lines:	3752

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💛 - Coveralls