Customizing the Search results UI in SharePoint 2013 Preview - Introduction

Quote Steve Peschka (MS): "SharePoint 2013 has a number of outstanding features that allow you to really use and customize search results like never before." ...
"In SharePoint 2013 – queue the music – we have display templates and what an improvement they are. No longer do you need to carry your XSLT Zen about you, now you can create your custom display code as straight HTML – yahoo!"

So let's try to find out how we are able to customize the search results user interface in the following web parts:

1. Refinement web part: show associated icons in front of the File extension refiner filters (part 1);
2. Refinement web part: show associated icons in front of the Result type refiner filters (part 2);
3. Search Results web part: add tumbnail view to the Display Template of the Result Type for images (part 3);
4. Hover Panel: add extra action to open the edit form of the item (part 4).

Preview of the customized Refinement panel:

Part 1 will explain in detail how this can be done.