[Wish] Show Output file path during encoding

[NetAktiv]

During encoding a video avidemux displays the name of the input file in the header and statistics of the output in a popup box. But the are no means to detect the name or path of the output file. The output filename additionally should be shown in the Details section of the output Statistic. For better usability this information is especially important if there running many instances of avidemux at the same time converting source files with identical names, for example VTS_01_1.VOB from different DVDs.