!per #3704 Persistence improvements

- Channel enhancements (#3773):
- Live read models (#3776):
- Batch-oriented journal plugin API (#3804):
- Batching of confirmations and deletions
- Message deletion enhancements (more efficient range deletions)
!cha #3789: Remove typed channels
Merge pull request #1915 from krasserm/wip-3704-persistence-improvements-part-1-krassserm

!per #3704 Persistence improvement (part 1)
!act #3812: Remove Pipelines
Merge pull request #1932 from drewhk/wip-3812-remove-pipelines-drewhk

!act #3812: Remove Pipelines
Merge pull request #1931 from drewhk/wip-3689-remove-typed-channels-drewhk

!cha #3789: Remove typed channels
=act #3572 Add parens to sender

* because it is not referentially transparent; normally we reserved parens for
  side-effecting code but given how people thoughtlessly close over it we revised
  that that decision for sender
* caller can still omit parens
+act #3586 #3807 Implement mandatory read throttling
Merge pull request #1929 from akka/wip-3572-sender-patriknw

=act #3572 Add parens to sender
=per #3820 Increase some test timeouts in persistence

* reproduced the problem with sleep in LeveldbStore
Merge pull request #1909 from drewhk/wip-io-read-throtting-drewhk

+act #3586 #3807 Implement mandatory read throttling
Merge pull request #1937 from akka/wip-3820-persistence-test-timeouts-patriknw

=per #3820 Increase some test timeouts in persistence
Merge remote-tracking branch: upstream/master