Superflat Generator Fixes

The superflat generator relied on an implicit include of server.hpp and using directive for the "MCPP" namespace from common.hpp, which was no longer included (since I've been removing references to common.hpp wherever I find them).

Fixed these problems, so it compiles again.
Remove Reference to common.hpp

Removed a reference to common.hpp from the chat login/logout broadcast module.
Remove common.hpp

Verified all references to common.hpp have been found and removed, and therefore (finally) removed it.
Time Update

Updated the time/tick manager module.  In addition to making it compatible with the changes made to the entire project in the wake of 1.7.x I significantly rewrote it, so it's much more readable/maintainable.

Also added a forgotten #pragma once, and a forgotten doxygen \file directive in time.hpp.

The /time command is now an information provider -- /info time -- and provides significantly more information.
Makefile Cleanup

Removed an include directive for test.mk from mods.mk.

test.mk should never have made it into the repo in the first place.  Committing this addition to mods.mk was likely an oversight to begin with.