Add codec and bitrate to watermark command line

Current implementation relies on FFMPEG default behaviour. By default fmpeg2 codec will be used to perform watermarking. That can lead to quality regression on some formats. For instance DNX HD is a high quality format and requires dnxhd codec to lossless processing.

Command line contribution should be changed to include codec and bitrate

<command name="videoWatermarkWithPicture" enabled="true">
            <commandLine>ffmpeg</commandLine>
            <parameterString>-y -i #{sourceFilePath} -i #{pictureFilePath} -c:v #{codec} -filter_complex #{filterComplex} -b:v #{bitrate} #{outFilePath}
            </parameterString>
            <installationDirective>You need to install ffmpeg.</installationDirective>
        </command>

Changing that behaviour will require changes on the packages that perform custom watermarking