Add Cancel button to job Configure Screen

The job configure screen needs a Cancel button. It currently only has Save and Apply.

This issue has been observed for the job configuration screens of the following:

1. freestyle
2. multi-configuration
3. multi-job
4. folder

It probably exists for others too.

This is needed so that a user can view a jobs configuration without actually changing the configuration.

I have observed that I can make zero(0) changes to a job and when I select Save to exit the configuration window, the corresponding config.xml is updated. The updates are often changing a plugin version, or sometimes removing empty XML statements and other times adding empty xml statements.

Another reason to add cancel is in the event that a user makes a modification that they don't want saved. The want to cancel the configuration session.

Moreover the Cancel button would only apply to unsaved changes. For example if the did the following:

1. Modify config
2. Select Apply
3. Modify config
4. Select Cancel

Then that would only back-out/revert/cancel the changes made for step 3 since it hadn't be applied yet.

I guess this might also be considered an Exit button.