Improve UX for handpicked blocks in editor

[perarnborg]

• [x] Clear search results and search text when a post is selected
• [x] Move custom controls to Block settings panel
• [x] Improve ux writing in panels and maybe panel names
• [x] When adding a new block a text that lets the editor know that the block is empty would be helpful
• [x] Redo list of selected posts, maybe use icons in stead of buttons for moving and removing posts. Drag and drop?
• [x] Double check handpicked panel in dynamic block
• [x] Display post type labels in stead of slug in search result
• [x] Improve design of how post type is displayed in search result. Use "pill" or something like that.