Improve management of zoom

[bwl21]

Request

Zoom is not consistent:

1. Autoscroll while playing only works in normal view
2. zoom steps should be by configuration
3. zoom is not maintained in systemstatus
4. zoom should be adapted also per perspective

solution appraoch

1. add zoom in configuration
2. replace literals
3. investigate autoscroll
4. implement zoom in a proper method / class