V3.9.4: Finetuning — Endless ATC Steam update #859613

A couple of fixes and adjustments: V3.9.3 (6 Feb 2019) Flow limit can be set up to 180 planes per hour. Before, the limit was 120/h, which may not be challenging enough when there are 3 landing runways available (like at KATL). However, the departure flow is unlikely to keep up with very high flow rates, depending on the runway configuration. More departures from secondary airports when flow mode is enabled. The amount of traffic to secondary airports actually depends on the skill value you have set. If you want high traffic rates at secondaries, set a high skill value before switching to flow mode. Flow mode sets the traffic flow to the main airport. Added wake turbulence information to the text at the bottom of the screen when the mouse cursor hovers above a near plane. Added a low contrast option, to reduce display issues on certain monitors (VA panels) with slow black->grey pixel tra...