Calendar DisplayableEditorView

DisplayableEditorView is the base class used for addEventDisplay and addCommitmentDisplay, and should only be called when initializing a tab for one of the two.

DisplayableEditorView(Boolean showEnd) will create a number of fields / ui displays for user input, including name, start date, description, participants and category by default. If showEnd is true, it also adds in a field for the end date of an event, while if showEnd is false it will add a field for the status of a commitment.

DisplayableEditorView is only responsible for creating the UI aspects and fields for the add/edit tab: the backend saving / updating / errorchecking is in the addEvent/CommitmentDisplay classes.