GROOVY-9133 Loop mode for groovy-console

[JacobAae]

This pull requests enables:

• Setting to enable loop mode in script menu
• If enabled run the code in a looping fashion with 1000 millis break after it has ended.
• Preference added to update the time between loops

Work started at GR8Conf EU 2019 Hacker Garden - with Credit to the group of https://github.com/karfunkel , https://github.com/sbglasius and https://twitter.com/a_taylor95 - And guidance from Paul King

[paulk-asert]

Thanks! Merged with a rename of prefs variable - hope that's okay.