Show "Add new" buttons over list on the right bottom corner

[tigert]

Is your feature request related to a problem? Please describe. The add new -buttons take vertical space from the list, and use only a small amount of space horizontally.

Describe the solution you'd like

• make buttons hover over the list, but place them on the right edge, over the "Actions" column
• Only show the context menu button when mouse is over a config item (related: #2304 ) so the right column is clear by default
• Add empty space to the end of the list so the last config's context menu can always be accessed. This is a compromise that for example Android uses and it seems to work fine.

Alternatively add them as combo so you dont need to click twice to add.

We could also have keyboard shortcuts I and O for adding new input and output config.

[DocMoebiuz]

I also like keyboard short cuts very much. That's a great idea.