Merge color and depth formats into PixelFormat
Add CompressedVector

... a std::vector with an additional enum storing the current compression type of the data.
Rename [de]compress() to better reflect what these methods are really doing
Add convenience methods to encode/decode a CompressedVector
Use a compressed vector as the buffer type for images and IBR-images
Use an image to implement the depth buffer in IBR images
Add JPEG compression using libjpeg-turbo
Add the possibility to specify the compression algorithm in Image and IbrImage. Default compression is JPEG for remote rendering and Snappy for IBR-rendering.
Fix JPEG decoding. Store information about the output image in JPEGOptions.
Requires libjpeg-turbo 1.2.0 or later Additionally double the size of the output vector each time the buffer needs to be flushed