Update missing suggested alternatives in deprecated JbpmSessionFactory

The class org.jbpm.db.JbpmSessionFactory is deprecated and the deprecation comment states: @deprecated use

{@link org.jbpm.tc.ContextBuilder}

and

{@link org.jbpm.tc.db.JbpmSessionContext}

instead.
However, the org.jbpm.tc package is no more in the code.
Thus, another suggested replacement should be provided.

Contrarily of as specified in http://jira.jboss.com/jira/browse/JBPM-624 this issue is not fixed in CVS (as the code was downloaded from CVS).