INT-3353 Concurrent RedisMetadataStore

JIRA: https://jira.spring.io/browse/INT-3353

Shared metadata for PersistentAcceptOnceFileListFilters.

INT-3353 Polishing; PR Comments
INT-3358: Make `MutableMessage` package protected

JIRA: https://jira.spring.io/browse/INT-3358
INT-3353 Fix Docbook White Space

JIRA: https://jira.spring.io/browse/INT-3355
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`.
It allow do not configure separate collections for different type of `MessageStore`