This is the last of the commits that hopes to enforce the distinction between "layout...

This is the last of the commits that hopes to enforce the distinction between "layout files" and "document classes" that was introduced by the modules code. For the most part, these changes just refactor code from TextClass between: (a) a TextClass base class; (b) a LayoutFile subclass, which represents the information in a .layout file; and (c) a DocumentClass subclass, which represents the layout information associated with a Buffer---a LayoutFile plus Modules. Methods from TextClass have been apportioned between the three classes depending upon what is needed where, and signatures have been changed where necessary so that the right kind of class is required.

At this point, there are no simple TextClass objects in the main LyX code, and it is impossible to create them, since the TextClass constructor is protected. Only LayoutFile and DocumentClass objects can be constructed, and for the most part these are constructed only by their respective containers: BaseClassList and DocumentClassBundle. There is an exception: LayoutFile does have a public default constructor, but if anyone knows how to make it go away, please do.

There will be one or two more commits along these lines, but these will be simple renamings. For example, BaseClassList should be LayoutFileList.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@23343 a592a061-630c-0410-9148-cb99ea01b6c8