Bug 33883: "Make sure to copy your API secret" message overlaps text

Bug 33883: "Make sure to copy your API secret" message overlaps text

This patch updates the markup on the patron API keys page so that it
uses standard classes for dialogs and page sections.

To test you must have RESTOAuth2ClientCredentials enabled.

- Apply the patch and locate a patron record.
- From their checkout or detail page, choose More -> Manage API keys
- Click "Generate a new client id/secret pair"
- Enter a description and click Save.
- You should see a message in a standard message-style dialog, "Make
  sure to copy your API secret now. You won’t be able to see it again!"
- The API key information should be displayed in a .page-section div.
- The table of existing keys should be displayed in a .page-section div.

Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: David Cook <dcook@prosentient.com.au>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>