Make import more explicit in some notbook section

reimport HTML and Image in some place so that each of the subsection can
be ran independently

Also, link to python logo from subfolder to make the example directory
more packager friendly. The actual png file will be added in next commit
copy IPython logo in example directory

request from pakagers to make the example directory more "standalone"
Merge pull request #3115 from Carreau/fix-example

avoid references to files outside of examples directory
    
request for packaging, it would be nice for example not to reference
files outside of example directory
copy ../../_static/logo.png in logo/logo.png
use subfolder for demo purpose of targeting subfolder in demo notebook