Fix SpecialSource version to 1.2.1 instead of 1.3 snapshot

API-incompatible changes in the works, so keep MCPC+ on the old
version until it can be updated in sync.
Add option to disable connection login logging. Closes #101.

New bukkit.yml setting: mcpc.connection-logging. Defaults off
to reduce console log spam when new users connect, but can be
enabled for debugging purposes or to see what mods users are
connecting with.