01_Application_Framework: 02_Application_Startup_Dbus: Refer to D-Bus activation

01_Application_Framework: 02_Application_Startup_Dbus: Refer to D-Bus activation

Creating a new application is as well quite specific to D-bus activation
so use a dedicated page for it, and modify the links that point to it.

Bug-AGL: SPEC-4700
Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: I3fd7174ac573e1670231570ff6422156b53e5a06
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/documentation/+/28525
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>