GitLab

Adds D2 developer's guide

Fixed the main page table of contents to include D2's sections as subpages
Minor word changes and clean up

Added src/bin/d2/images to image path in doc/Doxyfile
Added d2 subpage to doc/devel/mainpage.dox
Added the following:

Also, updated configure.ac to not reference removed files. The
--disable-dhcp and --disable-dns configuration flags have been removed.

Thsi is another test of git with new repo

This is mostly just a test of using new git repo for kea.

fixed many typos
also consistently spell and capitalize PostgreSQL.

as reported on dhcp jabber

(discussed a little on jabber)

(maybe this should be automatically set to current year)

(blame it on my broken laptop which randomly types simulated "x"
characters which is delete char in vi. I should have the diff reviewed!)