Added support for defining a "time range" for a Playable to set the time boundaries of what can be played by the diffenrent players (Popcorn and HtmlPlayer for now). Added option in Segment widget to define a timerange on click.

.Ldt-PlaceholderPlayer {
    font-size: 40px; text-align: center;
    padding: 40px 0; font-weight: bolder;
    background: #333333; color: #FFFFFF;
}