Ycbvideo

- the code base has been restructured to separate concerns better

- Allow for customized iteration of frames
- Disable caching of frames when using __getitem__

- *-meta.mat file data is now also accessible by frame objects
- bugs regarding range expressions and *-box.txt files are fixed

- parsing and processing of selection expressions is completely reimplemented, since the former solution was hard to maintain and bad
structured
- the YcbVideoLoader class is renamed to Loader
- the FrameDescriptor class is renamed to Descriptor
- the object returned by the frames() method now behaves list-like: the len() builtin and index-based element access are additionally supported
- the types Frame, Descriptor and Box are now exported in __init__.py

Path handling has very likely not worked on Windows in previous versions. The problem should be fixed now.

Two new selection expressions are supported:

- 'data' to specify all frame sequences except the data_syn frame sequence (i.e. all frame sequences contained in `data/`)
- range expressions allow for specifying ranges of frame sequences or frames, syntax and semantics are comparable to
how slicing works in Python