prepare pom.xml file for deployment into the JBoss Nexus

This pull-request is about making db_bootstrap ready to be deployed as artifacts in the JBoss Nexus repository. To be allowed to publish artifacts under the "org.wildfly.extras" you will have follow some guidelines https://developer.jboss.org/wiki/WildflyExtrasRepository
What about registering the module in standalone.xml ? Like so:
        <extension module="org.jboss.as.extension.db_bootstrap"/>
.. in the extensions xml block