CLI/launcher: improve error reporting
CLI: improve help's description of --persist
Fix rebind to app on catalog's classpath
rebind: remove duplicate prePreManage call
rebind: avoid ugly exception logging on shutdown
Rebind: catch exception generating memento

- so that other entity mementos will still be generated + persisted,
  even if one entity is faulty
Fix ExecutionManager.shutdownNow: stop all executors
Add brooklyn-persisted-state to .gitignore
persist: ensure delete really deletes file

- previously was bug where change-change-delete could cause the second
  file-change to be written after the delete, thus re-creating the
  deleted file.