Provides a text formatter add-on for an ITextViewer.
A text formatter changes the formatting of document region while
preserving and correctly updating the positions of the document.
Package Specification
IContentFormatter defines the concept of a text formatter. It
collaborates with content type specific formatting stratgies (IFormattingStrategy)
which for a given document region format the subregion with the matching
content type. The package contains a default implementation of IContentFormatter
(ContentFormatter).