Add utility application to convert any VisionX supported recording types

This MR features a simple terminal utility application to convert any VisionX supported recording file types into each other.

anon@anon:~/armarx/VisionX/build/bin$ ./cvtrec --help
cvtrec - VisionX utility to convert recordings

Usage: cvtrec input_file output_file
  input_file:  Path to input file
  output_file: Path to output file

Example: (To convert a PNG image sequence to AVI)
  `cvtrec /path/to/img/seq/ ./videofile.avi`

Arguments and options:
  -h [ --help ]         Show this message
  -p [ --progress ]     Print information about the conversion progress
  --in arg              Path to input file which should be converted
  --out arg             Path to output file where the converted recording 
                        should be written to

The are no API-breaking changes

Other changes:

• Add essential API to visionx::replay::Replay (getFrameCount)
• Add optional API's to visionx::replay::Replay (overloads for getNextFrame: Default method took a void*, but this resulted in not obvious RGB/BGR encodings of the images. The new APIs take cv::Mat and ::CByteImage instead, and can therefore apply the correct encoding. Documentation was changed in favour for the new APIs and the use of the void* API was discouraged)
• Fix a serious error in the conversion from cv::Mat to ::CByteImage (lead to segmentation faults)