Add more styling options for range date selection

Add new attributes: calendar month text size and text style.

Fix some internal issues

1. Add public methods for calendar appearance customisation.
2. Add the ability to determine whether a date is a weekend or not.
3. Internal upgrades and improvements.

1. Migrate from the legacy Support Libraries to the new AndroidX packages.
2. Add new public method (CalendarView.updateSelectedDates) for selected dates updating.
3. Rename SelectionMode.NON to the SelectionMode.NONE.

1. Add the ability to set the firstDayOfWeek in the setupCalendar() method.
2. Add the ability to set a onDateLongClickListener for the Calendar dates.
3. Add the ability to set a dateSelectionFilter that indicates whether a date available for selection or not.
4. Add an optional year selection control that allows to quickly navigate between years.
5. Add a calendarViewStyle attribute as a default value for defStyleAttr in the CalendarView constructor. So now it is possible to define common style for all Calendars in the application Theme file.
6. Change visibility level to internal of some library classes and interfaces.
7. Some internal cleanup and refactoring.