Directory specification for file watching (FileWatch.directoryExpr) can access environment variables

Feature

• The directory of a File Order Source that is used for file watching with Agents is notated as an expression that allows access to the Agent's environment variables..
• Examples in JSON
  • "directoryExpr": "env('HOME') ++ '/files/incoming'"
    • watch for files in a Unix environment using the HOME environment variable and sub-directories
  • "directoryExpr": "env('FILE_DIR', env('HOME')) ++ '/files/incoming'"
    • watch for files in a directory specified by the FILE_DIR environment variable and sub-directories. If the FILE_DIR environment variable does not exist then the HOME environment variable is used as a fallback.