Fix/low latency

[dsilhavy]

This PR addresses issues raised by @bbert on Slack:

• When playing in low latency mode: Ignore the duration of the segment when determining whether a new segment request shall be scheduled or not. Otherwise, we delay fetching chunks in low latency mode. See changes in ScheduleController
• Proxy the fastSwitchEnabled option through MediaPlayerModel. By default, this setting is now set to null. In case the app is not setting an explicit value we default to true for normal playback and false for low latency playback. In general, we should think about having a default configuration and a user provided configuration to avoid setting values to null by default. The reason we are doing this right now is to understand when a setting has been explicitly set by the application or when it is simply an untouched default setting.

[dsilhavy]

Merging this as potential additional changes will be made on top