Implement dask client.

[josuemtzmo]

Improvements:

• Support for dask client.
• Add useful links in user preferences.

Within the node tree, the dask dashboard is displayed.

The user preference allows the user to initiate blenderNC using dask.

[josuemtzmo]

Coverage will drop, as many of the implementations require changes in the user interface. However, changing the preference blendernc_use_dask is now tested.

[whatnick]

Dask worker temp files are checked in..please add these to .gitignore and git rm here.

[josuemtzmo]

Thanks, I completely forgot to remove them!

[josuemtzmo]

I removed the testing of dask, as currently running dask in background mode will generate the following issue, as a consequence of multiprocessing modifying the sys.path.

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/bin/2.92/python/lib/python3.7/multiprocessing/spawn.py", line 105, in spawn_main
    exitcode = _main(fd)
  File "/bin/2.92/python/lib/python3.7/multiprocessing/spawn.py", line 114, in _main
    prepare(preparation_data)
  File "/bin/2.92/python/lib/python3.7/multiprocessing/spawn.py", line 225, in prepare
    _fixup_main_from_path(data['init_main_from_path'])
  File "/bin/2.92/python/lib/python3.7/multiprocessing/spawn.py", line 277, in _fixup_main_from_path
    run_name="__mp_main__")
  File "/bin/2.92/python/lib/python3.7/runpy.py", line 263, in run_path
    pkg_name=pkg_name, script_name=fname)
  File "/bin/2.92/python/lib/python3.7/runpy.py", line 96, in _run_module_code
    mod_name, mod_spec, pkg_name, script_name)
  File "/bin/2.92/python/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/blendernc/tests/blendernc_nodetree_settings.test1.py", line 6, in <module>
    import bpy
  File "/bin/2.92/scripts/modules/bpy/__init__.py", line 38, in <module>
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    from _bpy import (
ModuleNotFoundError: No module named '_bpy'

I will look more into this, but I believe there will be no way to test this soon. A really interesting discussion on this issue can be found at:
TylerGubala/blenderpy#23

[josuemtzmo]

I figured that if the dask.Distributed.Client is initiated with the processes=False flag, then the issues disappear. This also solves BlenderNC crashing within the UI when loading a dataset and creating forks of the child processes.

[codecov]

Codecov Report

Merging #120 (6188bf7) into master (fb11443) will decrease coverage by 0.39%.
The diff coverage is 53.96%.

@@            Coverage Diff             @@
##           master     #120      +/-   ##
==========================================
- Coverage   72.33%   71.94%   -0.40%     
==========================================
  Files          39       39              
  Lines        2606     2666      +60     
  Branches      312      317       +5     
==========================================
+ Hits         1885     1918      +33     
- Misses        634      660      +26     
- Partials       87       88       +1     

Flag	Coverage Δ
unittests	71.94% <53.96%> (-0.40%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
blendernc/blendernc.py	100.00% <ø> (ø)
blendernc/panels.py	50.75% <37.50%> (-2.95%)	⬇️
blendernc/preferences.py	74.50% <61.11%> (-5.21%)	⬇️
blendernc/messages.py	73.58% <100.00%> (+1.58%)	⬆️

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