Transcoder : do not set output profile AND ICodec when adding generated stream

[valnoel]

When we want to generate a stream (black or silence), we should not have to set both output profile and ICodec. The ICodec should be guessed from the profile, which must contain enough parameters to generate the stream.
It would avoid duplicated parameters into ICodec and profile.

https://github.com/mikrosimage/avTranscoder/blob/develop/src/AvTranscoder/transcoder/Transcoder.hpp#L56
https://github.com/mikrosimage/avTranscoder/blob/develop/src/AvTranscoder/transcoder/Transcoder.hpp#L66

[cchampet]

Since a valid video/audio profile only get a codec name, we need more informations, stored in the ICodec (more exactly the xxxFrameDesc).
This is not a problem... Maybe we need to define constants in the code to define default video size, default pixel format, etc... ?