In order to enable future support for slide transitions has been needed

to
modify the part of the presentation engine handling the slides
navigation feature.

A new structure for slide and master page elements has been designed.
The following new classes have been implemented: MasterPageView,
TextFieldHandler, SlideNumberFieldHandler.
The following classes have been modified: MetaDocument, MetaSlide,
MasterPage, PlaceholderShape, Thumbnail.
The following classes have been modified and renamed: TextField ->
TextFieldContentProvider, FixedTextField -> FixedTextProvider,
VariableDateTimeField -> CurrentDateTimeProvider, SlideNumberField ->
SlideNumberProvider.