[0.5.0] Responsive template - Rebased

PR summary:

- New Responsive theme, Started here: #46
- New Slideshow Core Widget with demo slides
- New test page and a widget listing all form elements
- Navigation identity
- Now using semantic html5 tags
- Revised and fixed most of W3C form issues (mainly duplicated ids etc..)

B/C Status:

Anyone using own theme will need to revise it since this PR changes some top-level Core tags to more semantic.
Examples:
app/modules/Core/View/layouts/main.volt 
```<div class="container main_widget_container">``` changed to ```<main role="main">```

 app/modules/Core/View/layouts/widget.volt 
```<div class="widget_wrapper">``` changed to ```<article class="widget">```

 app/modules/Core/View/partials/layout.volt
```<div id="general-content-full-top">``` changed to ```<section class="content-top">```