Document various QtConsole embedding approaches.

Also added loading of default config to the in-process embedding example.
Correct the explanations for embedding.
Revert config-loading change in embedding example.
Clarify embedding in IPython; mention 4th method.
s/model_name/_model_name
s/Underscore/_
Improve description of Qt console embedding options
update components with font-awesome 3.2.1
font-awesome 3.2 moved resources
update css with font-awesome 3.2.1
mention msgspec versioning, and note v4.1 changes
msgspec version is 4.1
note v4.1 msg spec change in clear_output handler
make help menu a templates

add splitline after keyboard shortcut
float external-link icon to the right

and move the 'title' to the individual elements,
so it follows hover.
link to matplotlib latest.
remove alternate merge down shortcut

as shift+m is universal and sufficient
Merge pull request #4964 from ptone/merge-above

remove shift-= merge keyboard shortcut
Merge pull request #4939 from takluyver/embed-qtconsole-docs

Embed qtconsole docs (continued)
Merge pull request #4813 from Carreau/help-link

make help menu a template
Merge pull request #4982 from ellisonbg/slider-readout

Live readout for slider widgets