Navis

- added a lower-level `xform()` and `mirror()` function that requires transform(s)/mirror axis size as input
- new NBLAST variant `NBLAST_smart()`
- new io functions:
- `write_google_binary()` to write skeletons to Google's binary format
- `read_h5()` and `write_h5()` implement storing neurons in HDF5 files
- new function `merge_duplicate_nodes()` to de-duplicate nodes in skeletons
- new transform function: `symmetrize_brain()`
- `downsample_neuron()` now works on dotprops
- connectors are now included in a neuron's bounding box
- NeuronList division & multiplication now has a progress bar
- improve how HDF5 transforms deal with points outside the deformation field
- many small and big bug fixes

Check out the API docs to learn more about the new functions.

- massively speed up thin plate spine transforms
- hot fix for neuron's `.has_....` properties
- improved docstrings

This major release brings a new module for transforming data between template brains. Specifically, `navis` now supports affine, CMTK, HDF5 and thin plate spine transforms. Check out the new [transforms tutorial](https://navis.readthedocs.io/en/latest/source/tutorials/transforming.html) and the accompanying [flybrains](https://github.com/schlegelp/navis-flybrains) package.

Hot fix for Vispy viewer (issue with legend). Also some improvements to `navis.resample_neuron`.

Minor release with a few updates and changes to requirements to be more flexible with respect to the new pip dependency solver.

NBLAST-related bugfixes