Optional block templates for panel-header, panel-footer

[samselikoff]

I'd like to be able to add some html to my panel-header and panel-footer, something like this:

{{#bs-panel collapsible=true}}
  {{#bs-panel-heading}}
    Something here <span class='pull-right'>Ok</span>
  {{/bs-panel-heading}}
  {{#bs-panel-body}}
    My body
  {{#/bs-panel-body}}
  {{#bs-panel-footer}}
    Footer <span class='glyphicon glyphicon-camera'>
  {{/bs-panel-footer}}
{{/bs-panel}}

Would you be interested if I worked on a PR for this? I think we could still support the current API if users want text-only headers/footers.