UI/UX: Highlight active filters for inferences

[zven]

As pointed out here #151, the way the currently active inference filter settings might confuse the users.

At the moment, all filters are active, thus showing home, work and poi inferences. However, if the user deactivates some of those, nothing might be shown on the map or in the list. At the same time, apart from the actual toggle in the filter menu, the filter icon itself does not show any indication that there is a filter active. Plus: It's not highlighted that there are inferences that are in fact just not shown because some filters are active / not active.

For this, we potentially need to rethink the filter logic. Atm: If all filters are active -> everything is shown. If no filter is active -> nothing is shown. Maybe we should reverse that logic?

[zven]