Bug 22104: Clean up patron API keys template

Bug 22104: Clean up patron API keys template

This patch makes two corrections to the patron API key template: Convert
to Bootstrap grid and correct class on "new key" button.

To test, apply the patch and enable the RESTOAuth2ClientCredentials
preference.

 - Open a patron record in the staff client and choose More -> Manage
   API keys.
 - On the API keys page, confirm that the page adjusts well at various
   page widths.
 - Confirm that the size of the "Generate new client id/key pair" button
   matches the buttons in the toolbar.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>