Bug 32956: Use template wrapper for HTML customizations tabs

Bug 32956: Use template wrapper for HTML customizations tabs

This patch updates the HTML customizations template to replace tab
markup with the use of WRAPPERs.

- Apply the patch and go to Tools -> HTML customizations.
- Create or edit an entry.
- You should see tabs for each available language, for example
  Default, English, French.
- Test adding content to each language to confirm that the correct
  information is saved under the correct tab.

Signed-off-by: Philip Orr <philip.orr@lmscloud.de>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>