* ⇒, →, ←
* 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.
* backport of the timers from Akka Typed, #16742
* also fixed a small bug in FSM timers, which could result in that
a timer from a previous incarnation was let through to new
incarnation after restart
* no more need for the complicated "how to" section in docs of
how to schedule periodic messages
