Allow configuration of metadatastore

[sabbyanandan]

From @viniciusccarvalho on June 1, 2017 18:31

It would be nice to have support for pluggable metadata store like the aggregator has today:

java -jar aggregator-rabbit-1.0.0.RELEASE
               --aggregator.message-store-type=jdbc
               --spring.datasource.url=jdbc:h2:mem:test
               --spring.datasource.schema=org/springframework/integration/jdbc/schema-h2.sql

This would allow us to plug a metadata store that can keep tracks of files that have already been processed, avoiding reprocessing during restarts for example.

Copied from original issue: spring-attic/file#5

[sabbyanandan]

Closing this in favor of spring-cloud-stream-app-starters#45