Migrated Django app guide from parambokeh

[philippjfr]

This simply ports the user guide about embedding panel and bokeh apps, which was initially in parambokeh.

[codecov-io]

Codecov Report

Merging #241 into master will decrease coverage by 0.65%.
The diff coverage is 50.54%.

@@            Coverage Diff             @@
##           master     #241      +/-   ##
==========================================
- Coverage   90.02%   89.36%   -0.66%     
==========================================
  Files          34       44      +10     
  Lines        5354     5445      +91     
==========================================
+ Hits         4820     4866      +46     
- Misses        534      579      +45

Impacted Files	Coverage Δ
examples/apps/django2/sliders/bk_config.py	100% <100%> (ø)
examples/apps/django2/project/settings.py	100% <100%> (ø)
examples/apps/django2/sliders/views.py	20% <20%> (ø)
examples/apps/django2/sliders/urls.py	25% <25%> (ø)
examples/apps/django2/project/urls.py	33.33% <33.33%> (ø)
examples/apps/django2/manage.py	33.33% <33.33%> (ø)
examples/apps/django2/project/wsgi.py	50% <50%> (ø)
examples/apps/django2/sliders/bk_sliders.py	50% <50%> (ø)
examples/apps/django2/sliders/sinewave.py	55.55% <55.55%> (ø)
examples/apps/django2/sliders/apps.py	7.14% <7.14%> (ø)
... and 10 more

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