[*] Connected the alter entry use case to the GUI and added support for splitter bill.

[ScottCTD]

Summary

• I completely added support for alter entry use case and splitter bill.

Tasks

• [x] [*]Connected the alter entry use case with the GUI.
• [x] [+] Added a ConstraintTableCellEditor to constrain the value that a user can input to a table cell.
• [x] [*] Fixed some bugs in MySQLDatabaseGateway. @Lei-Tin
• [x] [*] Cleaned up some convention issues and optimized some imports in some classes.
• [x] [*] Added a global variable Main.DATETIME_PATTERN.
• [x] [*] Fixed the bug that the splitter bill columns do not change after switching.
• [x] [*] Fixed that the back button is enabled even in the normal bill.
• [x] [*] Added support of splitter bill in AlterEntryUseCase and DeleteEntryUseCase.
• [x] [*] Fixed the bug related to chaning the columns of the bill table.

[ScottCTD]

But I have a small question here, seems you did not use the alter entry input port in Main, is that necessary to import this interface? or this is just for convention?

I actually used AlterEntryInputPort.