INT-3338: MongoMS: Add `priority` and `sequence`

JIRA: https://jira.spring.io/browse/INT-3338

INT-3338: Add Docs

INT-3338: Make `priority` 'smart'

Add `Sort` for all group queries dependently of `priorityEnabled`.
Avoids the need to configure separate collections for different type of `MessageStore`

INT-3338: Add `MongoDbChannelMessageStore`

INT-3338: Polishing, Fixes, Improvements

Doc Polishing

Fix stream test.
INT-3367: Add `GemfireMetadataStore`

JIRA: https://jira.spring.io/browse/INT-3367

INT-3367 Polishing

Rename test class; move to metadata package; doc polishing.
INT-2975: Add `ValueExpression` for Typed SpEL

JIRA: https://jira.spring.io/browse/INT-2975

INT-2975: Add `type` attr. for enricher property

INT-2975: Check for `type`, polishing, docs

Enricher: deprecate property expression type attr
INT-2352 Support Control-Bus Atomic Router Updates

JIRA: https://jira.spring.io/browse/INT-2352

Add `replaceChannelMappings()` to the `AMMR`.

INT-2352 Polishing - PR Comments

Consolidate tests.
Fix up `@ManagedAttribute` Vs `@ManagedOperation`
Expose `setChannelMappings` over JMX