Customisation rework, finite scrolling & event data persistence

Breaking Changes:

• dayLabelLocaleIdentifier renamed to dayLabelLocale and is now of type Locale instead of String
• dayViewCellHeight renamed to dayViewCellInitialHeight
• Changes made to the colouring of current day view cells. It is now more simple and does what you tell it to, no more fancy logic based on the color of other days.

New features:

• EventData can be persisted using CoreData, see README for more details
• Scrolling can be set to be finite instead of infinite
• Can choose to hide the time overlay on the today DayViewCell