Move the gpg plugin to a profile
Move the gpg plugin to a profile

By moving the plugin to the sign profile the signing process
needs to be explicitly enabled (use -Psign).  This avoids
the need for a dummy key for local builds.

Closes #19

prestona/java-mqlight,mqlight/java-mqlight,prestona/java-mqlight,prestona/java-mqlight,mqlight/java-mqlight,mqlight/java-mqlight