Dcnum

- fix: properly propagate event extraction keyword arguments
- fix: QueueCollectorThread used uint16 for enumerating indices
- fix: handle case where number of events is not multiple of chunk_size
- enh: reduce thread waiting times
- enh: add bounds check for image cache

- feat: introduce QueueCollectorThread
- feat: introduce SegmenterManagerThread
- feat: instroduce EventExtractorManagerThread and corresponding workers
- enh: minor improvements for HDF5ImageCache and ImageCorrCache
- enh: use data size as cache size if smaller than requested chunk size
- enh: return dictionary for brightness feature computation
- enh: allow to pass a single image for brightness feature computation
- enh: allow to pass a single image for texture feature computation
- enh: make sure that masks are written as uint8 to HDF5 files
- ref: haralick texture computation now returns dict instead of recarray
- ref: renamed HDF5WriterThread to DequeWriterThread
- ref: renamed feature submodules (prepended "feat_")

- enh: dataset keyword arguments and mode HDF5WriterThread
- enh: speed-up of brightness feature computation

- feat: add HDF5Writer and HDF5WriterThread classes in write submodule
- feat: segmenters compute labeled images instead of masks
- enh: introduce iter_chunks for cached image data
- ref: do not filter for contour length
- ref: rename feat.background.get_available_background_methods
- ref: store PPID information in dataset metadata instead of "user" section

- enh: allow to set image_cache_size in HDF5Data
- enh: allow to easily register new custom segmenters
- ref: CPUSegmenter has its own submodule now

- feat: introduce HDF5 virtual dataset path concatenator
- enh: allow to pass h5py.File object to HDF5Data
- fix: typo in logging statement for sparse median bg computation