Improving hover actions and visualization on left and resources pane

[julioramosest]

We slightly improve "preview" and other important actions, file or resouce related, in both the left and the middle panes.

• Rework of layout for left and middle panes, hover visualization included. Also to unify hovering accross accordion tabs in left pane. Find exact layouting details in the figma below.
• Let's consider adding a main action for hovering the resources (maybe this is not needed)
• Adding options to three dots menu in resurces pane

Figma: https://www.figma.com/file/HOx9fsNedtkR2G0bCpHDX9/Resource-actions%2C-previewing-and-more?node-id=368%3A1234&t=tqtHrWZWeIMTLXKZ-1