Change FileDecoder init function input parameters and completely switch from uridecodebin to gnlurisource

- FileDecoder Init Input parameter are now (uri, start, duration)
    Default values for start and duration keep FileDecoder to decode the whole file
    - Default value for start is 0
    - Default value for duration is set to the remaining duration of the file after the start position
- No more use of uridecodebin : switch to gnlurisource to enable segment specification