Create partials for event pages

[mattstratton]

This wasn't an issue when we had only one template type, but with the addition of talks/single.html we have some repetition.

Generally speaking, this is what should go into
/themes/devopsdays-legacy/layouts/partials/event_header.html

{{/*
  This section is what creates the query to get at all the site data. If you need this somewhere, you can just copy
  it and paste it. Need to figure out if a partial would expose the variables/elements/array created herein. It could be done in a partial (need to include the trailing .) but I don't think it would work in shortcodes, which is where we need it the most - mattstratton
*/}}

{{ $path := split $.Source.File.Path "/" }}
{{ $event_slug := index $path 1 }}
{{ $event := (print .Params.year (lower .Params.city)) }}
{{ $e :=  (index $.Site.Data.events $event_slug) }}

{{/* end site data query */}}

<div class = "container-fluid">
  <div class="row">
        <div class="col-md-8">
      <h1> {{ $e.city }} {{ $e.year }} - {{ title .Title }} </h1>
      <!-- Main navigation -->
      <div class="submenu">
        <h3>
        {{ range $navigation := $e.navigationelements}}
          <a href="/events/{{ $event_slug }}/{{ $navigation}}">{{ $navigation }}</a>&nbsp;
        {{ end }}
        </h3>
      </div>

And this should go into /themes/devopsdays-legacy/layouts/partials/event_footer.html

    </div>



    <div class="col-md-4">
    <!-- sponsor code begin -->
    {{ $sponsors := $e.sponsors }}
    {{ range $e.sponsor_levels }}
    <h2>{{ .label }} Sponsors</h2>
      {{ range where $sponsors "level" .id }}
        {{ $s :=  (index $.Site.Data.sponsors .id) }}
        {{ if isset $.Site.Data.sponsors .id }}
          <a href = "{{ $s.url }}"><img alt = "{{ .id }}" src = "/img/sponsors/{{ .id }}.png" class="img-responsive company-logo" width = "95px"></a>
        {{ end }}
      {{ end }}
      <div class = "sponsor-cta">
        <a href = "/events/{{ $e.friendly }}/sponsor">Become a {{ .label }} Sponsor!</a>
      </div>
    {{ end }}

    <!-- sponsor code end -->
    </div>
  </div>

</div>
{{ partial "footer.html" . }}

Note that when you want to use the new partials, you will have to call them with the "dot" like so:

{{ partial "event_footer.html" . }}

[mattstratton]

OK, so this isn't super delightful, in that the variables don't get passed around between partials, so this bit of code:

{{ $path := split $.Source.File.Path "/" }}
{{ $event_slug := index $path 1 }}
{{ $e :=  (index $.Site.Data.events $event_slug) }}

has to exist in the template as well as both the event_header.html and event_footer.html template. It's still better than it was; I actually think that when we refactor the data directory in #133 this will change enough that it's not that big of a deal - this all exists just to get that last query, which will be made a lot simpler and more specific to where it is needed anyway. It will go from three lines to one in the data refactor.