A view that creates an index of files, and an index for each file.
First the index of files is created, intended for the top-left frame.
Second a view is created for each file, listing the major declarations for
that file, eg: classes, global functions, namespaces, etc.
Methods Details:
since FileTree generates a whole file hierarchy, this method returns the current filename,
which may change over the lifetime of this object
since FileTree generates a while file hierarchy, this method returns the current title,
which may change over the lifetime of this object
Registers a view for each file indexed.
Creates a view for each known file.
Creates a view for the given file. The view is just an index,
containing a list of declarations.