RFE: spec cleanup: make Core/Base follow conventions

[Jeff Johnson]

In lsbspec, the current convention is each submodule with libraries plus each
module have a directory. The submodule directories have the main content plus
an intro subdirectory that is used when making a submodule book. The module
directories have usually only an intro directory, which contains the
frontmatter for the module book - these are the official LSB specifications -
and glues the constituent submodules together.

The "with libraries" disclaimer is because submodule Toolkit_Independent (the
name since LSB 5.0) is handled inside the Desktop module directory as it has
only the xdg commands right now, it does not have its own submodule directory.
That should possibly be adjusted.

The original LSB specification, which is the Code module and the Base submodule
(which used to also be called Core), sits in a directory named LSB. It would
be more consistent if these were handled in the same way as the others - a
module directory Core, which would glue together the submodule directory Base
(renamed from LSB), the submodule directory Security, and the two "submodules
that are not official LSB submodules", ELF and Packaging.

This is listed as an RFE because it will be a fair bit of work, not clear if
it's worthwhile tackling it.

Note if the LSB -> Base rename is done, there are lots of pointers in both
lsbspec subdirectories as well as in books/booksets that refer to the location
LSB.