Generate developer docs with Sphinx

An effort was started some time ago to consolidate all internal
documentation in the git tree. However, this was just an accumulation of
files in various formats without any strucutre or way to browse it,
which results in no one even knowing that we have docs here.

This converts most of the files to restructuredtext and uses Sphinx to
generate an HTML browsable user manual (with a table of content and a
first attempt to put things in a global hierarchy).

There are almost no changes to the documentation content in this commit
(some obviously obsolete things were removed). The plan is to get the
toolchain up and running to make these docs easily available, and only
then see about improving the content. We can migrate some things off the
wiki and website, and rework the table of contents to have some more
hierarchy levels because currently it's a bit messy.

Change-Id: I924ac9dc6e753887ab56f18a09bdb0a1e1793bfd
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4370
Reviewed-by: Niels Sascha Reedijk <[email protected]>

docs/develop/busses/usb/USB_stack_design.rst

@@ -1,4 +1,4 @@
-INSIDE THE USB STACK
+The USB stack
 ==============
 
 For all of you who have been over my code and thought: "What is this guy doing?", I can firmly respond that I sometimes haven't a clue either. But when I'm actually reviewing my own code, I occassionally get the feeling that I do have a direction I'm persueing. In order to define this direction more, and share you in the fun, I have written this document. It's a rather superficial account (without actually quoting any code), but it should be enough to get you started.
@@ -15,4 +15,4 @@ New transfers are initialized by Pipes. The Transfer objects will be created by
 
 As for closing, this design lacks some objects that correspond to USB objects. For example, there are no special Endpoint objects. At the moment, passing adresses is sufficient, but perhaps it should change in order to complete the design. Also, there is currently no idea how locking should work. Finally, the Stack class currently includes some memory management for usb, however, checking from the specs, only UHCI requires manual scheduling, OHCI and EHCI manage the scheduling and packaging itself. That should move. But at the moment, this design works.
 
-Finally, this document gives an idea of how it should work. For details: check the USB specs, host controller specs and the code. If anything stays unclear, please comment on my weblog, or e-mail me.
+Finally, this document gives an idea of how it should work. For details: check the USB specs, host controller specs and the code. If anything stays unclear, please comment on my weblog, or e-mail me.