* ⇒, →, ←
* because we don't want to show them in documentation snippets and
then it's complicated to avoid that when snippets are
located in src/test/scala in individual modules
* dont replace object `→` in FSM.scala and PersistentFSM.scala
* Add CopyrightHeader support for sbt-boilerplate plugin.
* Add CopyrightHeader support for `*.proto` files.
* Add regex match for both `–` and `-` for CopyrightHeader.
* Add CopyrightHeader support for sbt build files.
* Update copyright from 2018 to 2019.
progressed with cleanup, removing the same thread exec context is
weird... causes issues :-/ Need to debug more, could be that some race
also exists in mapAsync then :\
WIP
finish ask impl via watch stage
mima
consistency spec
fix paradox, and fix adding ask/watch to javadsl source
follow up review
