Refactors picture filtering in admin backend and adds specs.

Moved the picture filter logic from controller to model.
Adds element name to class name selector of contents with custom tinymce config. Closes #400
Fixes page spec that expected that rails logger receives warn method.

We changed the way we log warnings in alchemy to rails debug log level in 94fcc4450339f1157f8b82fc65a25a0b429302ce

This fixes the spec for it.
JS escape validation error message when updating elements
Do not use fast_specs helper in test suite, because that breaks coverage.
Ensuring the correct rails version in alchemy executable.
Adds standard page layout file to scaffold generator.

Since we render the standard page layout as fallback to missing page layouts, we have to ensure that this file exists.
Refactors the way we handle initialization of element editors.

Fixes a lot of issues we had with (re)-initializing element editor views:

* The TinyMCE initialization is now aware of custom configurations
* The Element dirty observers now are universally bind to the Element.toggle event.
* A page onunload handler was added, that warns users if navigating away from pages with unsaved content.
Refactors the way we handle initialization of element editors.

Fixes a lot of issues we had with (re)-initializing element editor views:

* The TinyMCE initialization is now aware of custom configurations
* The Element dirty observers now are universally bind to the Element.toggle event.
* A page onunload handler was added, that warns users if navigating away from pages with unsaved content.
Close pleaseWait overlay, if page unload event is fired.
Remove console.log call in element toggle link.
Page timestamps are only updated when elements get saved not when get locked or unlocked.
Refactors the page users concern.

* Renamed the methods so they do not override method provided by userstamp gem.
* Take advantage of the methods the userstamp gem provides.
Update the userstamps when touching page.
Fix time comparision in page spec.
Compile alchemy.tinymce js module with all javascripts.

This improves performance. Please be sure to recompile assets after changing any tinymce settings.
Adds alt-q hotkey to leave admin area.
More robust specs for page lock! and unlock! methods.
Adds alt-i hotkey for info window in dashboard. [ci skip]
Fixes xml sitemap.