Navis

- native implementation of NBLAST: see `navis.nblast` and `navis.nblast_allbyall`!
- `plot3d` with plotly accepts a new parameter: if `hover_id=True` it will show its ID when hovering over a node
- a couple of bugfixes

Bug fixes and improvements for `Dotprops`:
- fix bug in creation (`navis.make_dotprops`) that lead to points wrong
- allow passing of dot props to `interfaces.r.xform_brain` and `interfaces.r.mirror_brain`
- new method: `recalculate_tangents`

Fixes a critical bug when plotting volumes using the Plotly backend. Plus a bunch of small bugfixes.

Lots of new stuff, improvements to existing functions and tons of bug fixes:
- new 'color_by' and 'shade_by' parameters for `plot2d` and `plot3d`
- make `NeuronLists` pickleable
- new functions: `insert_nodes` and `remove_nodes` to insert/drop nodes from `TreeNeuron` without disconnecting the neuron
- new function: `resample_along_axis` resamples `TreeNeurons` such that you get nodes exactly in provided intervals
- total reworks of topology related functions `strahler_index`, `segregation_index`, `bending_flow`, `flow_centrality` and `split_axon_dendrite`
- new topology function: `arbor_segregation_index`
- fix some bugs in the VisPy viewer
- total rework of `Dotprops` - now a subclass of `BaseNeuron`
- added functions to read and write Dotprops from/to `.nrrd` files
- new module `models` currently featuring a network `TraversalModel`

- allow mesh-like objects for certain functions (e.g. `in_volume` or `plot3d`)
- a couple small bug fixed

Lots of under-the-hood improvements and bug fixes. Most notably:
- reworked interface with R's nat.nblast
- improved (read: orders of magnitude faster) `stitch_neurons` and `heal_fragmented_neuron`
- under the hood changes to neuron property caching

See [here](https://navis.readthedocs.io/en/latest/source/whats_new.html) for the full change log.