Move the subitems from install->Advanced topics to customized_image
Add the subimtes for Advacned_topics
Add the subitems for discovery
Add subitems for developers
I moved the [Hardware Architectures] to [Manage Clusters] since I
thought the name [Hardware Architectures] will make user confusing
that this page is for hardware things.
Another change was I moved the kvm part to be a sub-doc of specific
arch. This is because the kvm only can be done after the bare-metal
deployment. In the kvm part, I'd like only includes the [host install]
and [vm management]. The OS deployment should be same with bare-metal.
And since there's no much customer were using kvm, move it to low level
will make our doc more clear to follow.
