Update documentation for classes split

* Make reference to meta/classes* instead of just meta/classes
* Update each reference to the path where the class has moved
* Add a brief explanation to the classes reference explaining the split
* Add a note to INHERIT, INHERIT_DISTRO, IMAGE_CLASSES and USER_CLASSES
  variable glossary entries mentioning where the specified classes must
  be located. I contemplated adding the same note to PACKAGE_CLASSES
  but decided against it, as it has a very specific usage and such a
  note might distract from the narrative of that entry.
* Also trim the IMAGE_CLASSES entry which was quite outdated.
* INHERIT += no longer works with testimage so drop the note about that

(From yocto-docs rev: e76bed00b452d3049f6c22afbfb980b557a141bd)

Signed-off-by: Paul Eggleton <paul.eggleton@microsoft.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/documentation/ref-manual/structure.rst b/documentation/ref-manual/structure.rst
index 533745b370..fe27d17caa 100644
--- a/documentation/ref-manual/structure.rst
+++ b/documentation/ref-manual/structure.rst
@@ -669,10 +669,10 @@ Yocto Project. Metadata has several important subdivisions:
 
 .. _structure-meta-classes:
 
-``meta/classes/``
------------------
+``meta/classes*/``
+------------------
 
-This directory contains the ``*.bbclass`` files. Class files are used to
+These directories contain the ``*.bbclass`` files. Class files are used to
 abstract common code so it can be reused by multiple packages. Every
 package inherits the :ref:`ref-classes-base` file. Examples of other important
 classes are :ref:`ref-classes-autotools`, which in theory allows any