Make placeholders less bright and add transparent mode

Problem/Motivation

Current placeholders look too dark for the initial load, would be good to make them lighter.

Proposed resolution

Also, when we reload the content (eg when clicking on facets) - it's better to keep the current content visible, but grayed out with animation, instead of replacing it with full gray squares. And maybe slightly blur the content, something like this:

So, the task is to make placeholders design more cool.

For the placeholders, we use this library http://github.com/MurzNN/placeholderify and seems we need to extend it by adding styles.

So, make and propose your vision.