As a JIRA Administrator, I need to be able to load Conditions and Validators from source files so my whole ScritpRunner customization can be code reviewed and deployed to a file system

Currently you can only load listeners etc via a Script File, not validators etc in Post Functions 

Everywhere where load conditions etc. we need to ensure that you can choose from a file on the FS 

Acceptance criteria: 

• In all conditions in ScriptRunner for JIRA, you have the same dialog as for Script Console (both an inline editor and a choice of a script file) 
• All associated assumptions about the editor works as expected: 
  • if file is not found, error is returned
  • if there is an error in the script file
  • editor will show which script roots are available 
• Ensure that backwards compatibility holds