As a user, I can choose the columns to show in the Test Runs List gadget

As a user, I can choose the columns to show in the Test Runs List gadget, using the gadget's settings.

 The available fields are:

• Test issue fields (eg. Summary, Key, Component, Priority, etc.)
• Test Execution Fields
  • Key (as it is currently displayed)
  • Fix Version
  • Revision
  • Test Environments
• Dedicated Test Run Fields
  • Assignee
  • Executed By
  • Comment
  • Start Date
  • Finish Date
• Test Run Custom Fields

It should be possible to add or remove columns from the available fields.

The columns shall be presented in the same order as they are defined in the settings.