sphinx: Organize top level docs

Clean up the top level docs index to refer to all the manuals
with decent titles/links/layout and match the current website docs
page links.

(From yocto-docs rev: 45138057bf9446dfca7bf1ddef97104df57abe76)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/index.rst

@@ -10,16 +10,41 @@ Welcome to The Yocto Project's documentation!
 
 .. toctree::
    :maxdepth: 1
+   :caption: Introduction and Overview
+
+   Quick Build <brief-yoctoprojectqs/brief-yoctoprojectqs>
+   What I wish I'd known about Yocto Project <https://www.yoctoproject.org/docs/what-i-wish-id-known/>
+   Transitioning to a custom environment for systems development <https://www.yoctoproject.org/docs/transitioning-to-a-custom-environment>
+   Yocto Project Software Overview <https://www.yoctoproject.org/software-overview/>
+   Tips and Tricks Wiki <https://wiki.yoctoproject.org/wiki/TipsAndTricks>
+
+
+.. toctree::
+   :maxdepth: 1
+   :caption: Manuals
+
+   Overview and Concepts Manual <overview-manual/overview-manual>
+   Reference Manual <ref-manual/ref-manual>
+   Board Support Package (BSP) Developer's guide <bsp-guide/bsp-guide>
+   Development Tasks Manual <dev-manual/dev-manual>
+   Linux Kernel Development Manual <kernel-dev/kernel-dev>
+   Profile and Tracing Manual <profile-manual/profile-manual>
+   Application Development and the Extensible SDK (eSDK) <sdk-manual/sdk-manual>
+   Toaster Manual <toaster-manual/toaster-manual>
+   Test Environment Manual <test-manual/test-manual>
+   Bitbake User Manual <https://link to bitbake manual FIXME>
+
+.. toctree::
+   :maxdepth: 1
+   :caption: 'Mega' Manual
+
+   All-in-one 'Mega' Manual <https://www.yoctoproject.org/docs/@VER@/singleindex.html>
+
+.. toctree::
+   :maxdepth: 1
+   :caption: Manuals/Variable Index
 
-   brief-yoctoprojectqs/brief-yoctoprojectqs
-   overview-manual/overview-manual
-   bsp-guide/bsp-guide
-   ref-manual/ref-manual
-   dev-manual/dev-manual
-   adt-manual/adt-manual
-   kernel-dev/kernel-dev
-   profile-manual/profile-manual
-   sdk-manual/sdk-manual
-   toaster-manual/toaster-manual
-   test-manual/test-manual
    genindex
+
+
+