INT-2881: Add support for the firstRecord to retrieving JPA gateway

A use case where the database being polled by the inbound adapter was read only and hence update/delete after poll was not possible. Getting whole data in memory was not a feasible option. Since inbound adapters were stateless, gateways were a better fit to the situation , however they lacked the support for getting the records from a provided from record prohibiting their usage. This JIRA http://jira.springsource.org/browse/INT-2881 is meant to address this shortcoming and the PR is a solution to this new feature.