[Collection] Contributions from Ellen

[Ellen141319]

The following is a list of PRs that I have completed:

• [+] Add deleteEntry Usecase #39
• [+] Extend the InsertEntryUseCase that can insert a new splitter entry. #65
• [+] Added javadoc for DeleteEntryUseCase #74
• [+] Use LGoodDatePicker.DatetimePicker to edit the date  #83
• [*] Improved the add entry dialog and added support for splitter entry. #90
• [+] add DeleteEntryUseCaseTest #111

Issues I participated in:

• [Feature 3] Implement Use Cases in our CRC Model. #7
• [Feature 7] Design and Implement Bill Splitter. #11
• [Improvement 3] Adding Javadoc everywhere #44
• [Feature 11] Extend the InsertEntryUseCase #51
• [Feature 12] Design and Implement How to add an Entry. #52
• [Documentation] Javadoc for DeleteEntryUseCase @Ellen141319 #57
• [Feature] Use some datetime picker to edit the date. #79
• [Feature] Add support for adding a splitter entry. #80
• [Improvement] Create a separate class for the dialog of adding an entry. #81