Fixes and doc updates for bundling machinery

[philippjfr]

Fixes #1653

[codecov]

Codecov Report

Merging #1655 into master will decrease coverage by 0.31%.
The diff coverage is 61.92%.

@@            Coverage Diff             @@
##           master    #1655      +/-   ##
==========================================
- Coverage   85.41%   85.10%   -0.32%     
==========================================
  Files         148      148              
  Lines       16840    16945     +105     
==========================================
+ Hits        14384    14421      +37     
- Misses       2456     2524      +68     

Impacted Files	Coverage Δ
panel/tests/test_server.py	100.00% <ø> (ø)
setup.py	0.00% <0.00%> (ø)
panel/io/notebook.py	57.98% <12.50%> (-1.16%)	⬇️
panel/compiler.py	11.42% <16.12%> (+6.77%)	⬆️
panel/io/resources.py	79.72% <81.48%> (-12.34%)	⬇️
panel/models/ace.py	95.23% <83.33%> (-4.77%)	⬇️
panel/models/echarts.py	92.30% <83.33%> (-7.70%)	⬇️
panel/models/plotly.py	95.83% <83.33%> (-4.17%)	⬇️
panel/models/vega.py	91.66% <83.33%> (-8.34%)	⬇️
panel/models/vtk.py	98.38% <83.33%> (-1.62%)	⬇️
... and 15 more

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