doc: Misc Windows doc formatting fixes

doc: Misc Windows doc formatting fixes

There are a couple of minor issues with this document:

- Some commands intended to be run in the MinGW shell are prefixed with
  '>', suggesting they are in fact PowerShell commands
- PowerShell syntax highlighting is not enabled
- Indentation is off for a couple of blocks

Resolve all of these through use of the 'code-block' element and a lot
of random fixes.

Signed-off-by: Stephen Finucane <stephen@that.guru>
Signed-off-by: Ben Pfaff <blp@ovn.org>