Allow user to opt-out of sending system information with uninstall feedback

[WesleyBranton]

Currently, the uninstall feedback page includes very basic information about the user's system. This includes whether they are using a Firefox or Chromium browser and the version of the add-on they are using. Both of these data points are helpful for tracking down issues and changes that should be made.

The user is informed prior to sending the feedback that this information will be included. They are also able to see this information prior to sending.

The user should be able to opt-out of sending this information with their user feedback.

[WesleyBranton]

The necessary changes were made to the web server. No add-on update is required.