dev-manual, Makefile: Created new section on multi-config build deps

Rewrote the section on setting up and executing multi-config builds.
Broke the section into two sub-sections.  One is for the standard
information that was there for setting up a multi-config build. A
new section was for the cross-build dependencies in multi-config
builds.

Part of the re-write included creating a new figure that shows
the configuration file hierarchy needed for these types of builds.
So, new figure added to both the dev-manual and the mega-manual
figures directories.

Finally, the Makefile needed updated to account for the new figures.

(From yocto-docs rev: dc158e97c216aa6e7fa3755164409d581f8569c5)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/Makefile

@@ -165,6 +165,7 @@ TARFILES = dev-style.css dev-manual.html \
 TARFILES = dev-style.css dev-manual.html figures/buildhistory-web.png \
            figures/dev-title.png figures/buildhistory.png \
            figures/recipe-workflow.png figures/bitbake-build-flow.png \
+           figures/multiconfig_files.png \
            eclipse
 	endif
 
@@ -261,7 +262,7 @@ TARFILES = mega-manual.html mega-style.css \
         figures/image-generation.png figures/key-dev-elements.png\
 	figures/sdk-generation.png figures/recipe-workflow.png \
 	figures/build-workspace-directory.png figures/mega-title.png \
-	figures/toaster-title.png figures/hosted-service.png \
+	figures/toaster-title.png figures/hosted-service.png figures/multiconfig_files.png \
 	figures/simple-configuration.png figures/poky-reference-distribution.png \
 	figures/compatible-layers.png figures/import-layer.png figures/new-project.png \
 	figures/sdk-environment.png figures/sdk-installed-standard-sdk-directory.png \