Bug 35877: Use template wrapper to build Bootstrap accordion components

Bug 35877: Use template wrapper to build Bootstrap accordion components

This patch adds Template::Toolkit WRAPPER blocks to html_helpers.inc so
that templates can build Bootstrap accordion components while keeping
the Bootstrap structural markup separate.

Each individual component of a Bootstrap accordion interface is defined:

- Group container
  - Collapsible item
    - Item heading
    - Item content

Included is a usage example:

    [ WRAPPER accordion id="accordion container id" ]
        [ WRAPPER accordion_item ]
            [ WRAPPER accordion_heading panel_id = "panel id" ]
                [Clickable panel heading ]
            [ END ]
            [ WRAPPER accordion_panel panel_id = "panel id" ]
                [Expanding content panel]
            [ END ]
        [ END ]
    [ END ]

To test, apply this patch and one of the dependent patches.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>