Enable keyboard navigation in resource browser

[Florian Schepers]

Is your feature request related to a problem? Please describe.
Currently, navigating the resource tree requires the users to click on each resource to expand/collapse.
For the user that implies the need to click a lot.

Navigation:

• up-down navigation with arrows
• use horizontal navigation to expand/collapse leaves
• experiment if it's better to select the item with space or if an item should be immediately selected after the navigation event

Describe the solution you'd like
As a user navigating in the file tree in resource view, I want to be able to use keyboard navigation.

is blocked by #971