Move dual indexing docs into management section
Add architectural overview documentation page
Minor doc tweaks
Adding architecture diagram

Meant to include this in 9cd7d080c09c1a0fc35ff549cd760e3574c2859a
Automatically generate AsciiDoc config reference
Folding titan-site into titan-dist

titan-site's old functions are being absorbed into titan-dist

titan-site had some usefulness way back when we combined the javadoc
for multiple modules when generating release javadocs, but now that we
only generate titan-core javadoc for releases, it has no real reason
to exist
Tweak Maven javadoc plugin configuration