InputFile: refactore readNextPacket
InputFile / AvInputStream: rename functions about buffer

* AvInputStream
    * Rename setBufferred to activate.
    * Rename getBufferred to isActivated.
* InputFile
    * Rename readStream to activateStream.
    * Rename getReadStream to isStreamActivated.
* Update apps and pyTest.
FileProperties: remove SWIG warnings

Avoid warning messages when SWIG has access of these overload functions
(const).
GeneratorVideo: set type of data to char
Pixel: fix init from AVPixelFormat

Correctly set BigEndian, Alpha, and Planar flags.
VideoTransform: fix fill plane data pointers

* Error for subsampling YUV420 in init when fill in cumulSrcOffset.
* Use FFmpeg function av_image_fill_pointers instead of manage it in our
code.
* Remove unecessary _srcOffsets and _dstOffsets.
Add SWIG interface for frame classes
AvInputAudio: clean readNextFrame
InputFile: clean

* Clean documentation.
* Move static method.
* Remove unecessary getProperties with parameter.
Frame: add function copyData
Merge pull request #17 from cchampet/fix_videoTransform

Fix videoTransform