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/components/header-content.hbs

@@ -1,5 +1,5 @@
 <section class="gh-header is-{{#match headerStyle "Magazine"}}magazine{{else match headerStyle "Highlight"}}highlight{{else}}classic{{/match}}{{#if @custom.background_image}}{{#if @site.cover_image}} has-image{{/if}}{{/if}} gh-outer">
-        
+
     {{!-- Background image --}}
     {{#if @custom.background_image}}
         {{#match headerStyle "!=" "Magazine"}}
@@ -64,7 +64,7 @@
         {{!-- Landing layout --}}
         {{#match headerStyle "Landing"}}
             <h1 class="gh-header-title is-title">{{#if @custom.header_text}}{{@custom.header_text}}{{else}}{{@site.description}}{{/if}}</h1>
-            {{> "email-subscription"}}
+            {{> "email-subscription" email_field_id="header-email"}}
         {{/match}}
 
         {{!-- Search layout --}}