Merge pull request #488 from robinboening/language_notice

Changes error on Language from base to certain attributes
Adds example of `alchemy_roles` method to README
Fixes preview scripts for pages not having jquery.
Fixes position of element status icon.
Compare resources search query to lowercase column value. Closes #493
Set I18n.locale in BaseController. Closes #492

We must not change the app's locale globally.
Refactors essence validations.

Splits the huge essence_validations method into smaller parts.