Various design improvements (#42)

There are a couple of minor improvements which customers solve at the moment with various hacks and should be part of the theme instead.

* Removed max-width from card excerpt

* Updated custom theme settings

- Added show/hide "Read more" section in posts
- Added drop-cap option for posts
- Added show/hide metadata for posts

* Added lock icon for members-only posts on list

* Updated excerpt logic to work with access levels

* Fixing missing id's for input fields

* Updated secondary color contrast

partials/post-card.hbs

@@ -21,10 +21,20 @@
                 <p class="gh-card-tag">{{primary_tag.name}}</p>
             {{/if}}
             <h3 class="gh-card-title is-title">{{title}}</h3>
-            {{#if excerpt}}
-                <p class="gh-card-excerpt is-body">{{excerpt}}</p>
+            {{#if custom_excerpt}}
+                <p class="gh-card-excerpt is-body">{{custom_excerpt}}</p>
             {{/if}}
-            <footer class="gh-card-meta"><!--
+            {{#unless custom_excerpt}}
+                {{#if excerpt}}
+                    <p class="gh-card-excerpt is-body">{{excerpt}}</p>
+                {{/if}}
+            {{/unless}}
+            <footer class="gh-card-meta">
+                {{#unless access}}
+                    {{^has visibility="public"}}
+                        {{> "icons/lock"}}
+                    {{/has}}
+                {{/unless}}<!--
              -->{{#if @custom.show_author}}
                     <span class="gh-card-author">By {{#foreach authors}}{{#if @first}}{{name}}{{else}}, {{name}}{{/if}}{{/foreach}}</span>
                 {{/if}}