Version 1.2.0

What's new:

• new function: navis.betweeness_centrality
• new function: navis.combine_neurons to simply concatenate neurons
• new set of persistence functions: navis.persistence_vectors, navis.persistence_points and navis.persistence_distances
• improvements to various functions: e.g. navis.bending_flow, navis.flow_centrality, navis.split_axon_dendrite and
  navis.longest_neurite
• navis.read_swc now accepts a limit parameter that enables reading on the the first N neurons (useful to sample large collections)
• navis.write_nrrd and navis.read_nrrd can now be used to write/read Dotprops to/from NRRD files
• navis.nblast (and variants) now accept a precision parameter that allows setting the datatype for the matrix (useful to keep memory usage low for large NBLASTs)
• navis.simplify_mesh (and therefore navis.downsample_neuron with skeletons) now uses the pyfqmr if present (much faster!)
• improved the interface to Neuromorpho
• added a new interface with the Allen Cell Types Atlas (see navis.interfaces.allen_celltypes)
• myriads of small and big bugfixes

Thanks to @clbarnes and @Robbie1977 for contributing various PRs!