Replace smallDNS with CMASS

[maxsvetlik]

CMASS was developed several years ago as a replacement for smallDNS. It contains a superset of features so I believe it replacing smallDNS could be quite simple, without major disruption to systems that rely on it.

Code is on this branch and should be tested thoroughly before deploying as production code.

I have run CMASS on nixons-head in parallel with smallDNS and can confirm it runs and gives valid, expected responses to simple requests.