Add chmod post-action

[mlorbetske]

Short term fix for #1028 - adds a post-action for calling chmod

Usage:

{
      "condition": "(OS != \"windows\")",
      "description": "Update permissions",
      "manualInstructions": [ ],
      "actionId": "cb9a6cf3-4f5c-4860-b9d2-03a574959774",
      "args": {
        "+x": "*.sh"
      },
      "continueOnError": true
    }

or

{
      "condition": "(OS != \"windows\")",
      "description": "Update permissions",
      "manualInstructions": [ ],
      "actionId": "cb9a6cf3-4f5c-4860-b9d2-03a574959774",
      "args": {
        "+x": [
          "*.sh",
          "somethingelse"
        ]
      },
      "continueOnError": true
    }