navigate through project overview using arrow keys

right now when you navigate in the project overview in the list of projects, it is  possible to use e.g. the arrow-down key only once, when you use it again, the task(s) are in focus and you can move through them (if more than 1)

this should be changed

• with arrow up and down you move through the projects
• only when you change the focus to tasks manually arrow up and down should move through the tasks