[FrameworkBundle] Fix server start in case the PHP binary is not found
Merge branch '2.6' into 2.7

* 2.6:
  Update filesystem readme.md to include exists method
  Add machine readable events
  Fixed minor typo
  [FrameworkBundle] Fix server start in case the PHP binary is not found
  Update UPGRADE-2.6.md
  [HttpKernel][2.6] Adding support for invokable controllers in the RequestDataCollector
  fixed typo
  [Translations] Added missing Hebrew language trans-unit sources
  [DependencyInjection] inlined factory not referenced
  Fixed case for empty folder
  Fixed whitespace control for password form widget
  [Routing] correctly initialize condition as string