Using custom animation play mode in LidarView

The current behavior of LV is to override the animation PlayMode and Duration settings when clicking on Play/Pause buttons. Therefore, it is not possible to use custom animations modes or settings.

The aim of this MR is to :

• change the behavior of the Play/Pause buttons so that they only invoke play/pause commands as expected
• change animation play mode and duration only if necessary when UI speed factor combo box is changed by user or if a dataset with new timesteps is loaded
• synchronize the UI speed factor combo box with real animation play mode so that it reflects the correct animation state
• avoid changing the apparent behavior of the UI

NOTE : When upgrading LVCore in your specific LidarView based application, you should consider removing the line app.scene.UpdateAnimationUsingDataTimeSteps() in function applogic.openPCAP(). Without this change, the speed mode will be set to All Frames when a new pcap will be loaded. By removing this line, the speed mode and animation settings won't be changed, and will be kept as user set them before.

@melanie.carriere @nick.laurenson @lea.vauchier PTAL