Add ability to set executable to an external application

[platysma]

Fixes #1084

Summary

Added ability to set executable to an external application by providing a filePath in the Run Action

Changes

Added additional field filePath in the Run Action. If set, a PathRunnable will be created in the Run Action.

schemes:
  ExampleScheme:
    run:
      filePath: /Applications/Example.app

[freddi-kit]

It looks good, please check my comments. Sorry for late