Update Mojo and services documentation

This is a large update to all Mojo and services documentation in the
tree. Here are the changes in a nutshell:

- Images for Mojo docs are upstreamed instead of being pulled from
  docs.google.com
- Various minor updates, corrections, clarifications in core Mojo
  docs
- Consolidation of documents in the tree.
- Refresh of all service and Service Manager related documentation,
  removing lots of outdated information, adding clarifying definitions
  and examples of core concepts

As of this CL, the relevant documentation in the tree is pared down
to:

- The mojo/ subtree itself
- services/README.md - service guidelines
- services/service_manager/README.md - general service manager
  and service API documentation, examples, etc
- docs/mojo_and_services.md - intro to mojo & services for
  chromium developers
- docs/mojo_ipc_conversion.md - advice for converting legacy IPCs
  to mojo interfaces
- docs/servicification.md - advice for servicifying chromium
  features specifically

Specifically this wipes out content/public/common/services.md,
ipc/README.md, services/service_manager/service_manifests.md, and
services/api_standards.md. Any still-relevant content that was in
these docs has been merged into one of the docs listed above.

Finally, the presence in docs/README.md has been cleaned up a bit.
A new section for "Mojo & Services" is added with links to the above
list of documents.

Change-Id: I294a32025afdca62441d3605da51d714f3aebd00
TBR: [email protected]
Reviewed-on: https://chromium-review.googlesource.com/c/1441640
Commit-Queue: Ken Rockot <[email protected]>
Reviewed-by: Oksana Zhuravlova <[email protected]>
Cr-Commit-Position: refs/heads/master@{#629384}
diff --git a/docs/README.md b/docs/README.md
index 933f296..9939e5c6 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -340,7 +340,20 @@
     install Chromium OS on VMWare.
 *   [User Data Directory](user_data_dir.md) - How the user data and cache
     directories are determined on all platforms.
-*   [Mojo](../mojo/README.md) - IPC mechanism used by services.
+
+### Mojo &amp; Services
+*   [Intro to Mojo &amp; Services](mojo_and_services.md) - Quick introduction
+    to Mojo and services in Chromium, with examples
+*   [Mojo API Reference](/mojo/README.md) - Detailed reference documentation for
+    all things Mojo
+*   [The Service Manager &amp; Services](/services/service_manager/README.md) -
+    Services system overview, API references, example services
+*   [Service Development Guidelines](/services/README.md) - Guidelines for
+    service development in the Chromium tree
+*   [Servicifying Chromium Features](servicification.md) - General advice for
+    integrating new and existing subsystems into Chromium as services
+*   [Converting Legacy IPC to Mojo](mojo_ipc_conversion.md) - Tips and common
+    patterns for practical IPC conversion work
 
 ### Probably Obsolete
 *   [TPM Quick Reference](tpm_quick_ref.md) - Trusted Platform Module notes.