As part of the architecture guide work for WiredTiger (PM-1529) it makes sense to reorganize the top level of documentation as described in the technical design.

What is currently in "WiredTiger Architecture" should be renamed "Overview and Features".  We'll create a new "WiredTiger Architecture" section that will be populated initially with parts (schema operations, data handle lifecycle) of "Developer Documentation".  We should make a cursory top-level page for this section that will be expanded more fully in a later ticket.  Other items from "Developer Documentation" will appear in a new section "Tools and Techniques" that will also have coverage of the wt command line.

This should be done first, before other edits or changes.  Having this in place first will let us do later documentation work in parallel.