Fix indentation of directive arguments

arguments must not be indented with tabs
Post about akka-persistence testing: journal-recovery
Post about akka-persistence testing: recovery from snapshots
Add tests for journal migration

This includes
- refactoring of WithItemApplication to differentiate between start
  and restart
- an App to save the journals
- a saved journal of a fictitious 0.1 release
Prelim post about akka-persistence and migration