Adding ITK docset

[get9]

I'd like to add the Insight Toolkit documentation to Dash. However, it's a fairly large toolkit with extensive documentation. The compressed version of the docset is 2.3 GB. I can shrink that down probably by two thirds by excluding inheritance maps and collaboration diagrams included on every class doxygen page like this, but by my calculations it will still be very much above the 100 MB limit. Any suggestions on how to add this to Dash?

[Kapeli]

Just make a pull request containing everything except the actual docset tgz, and upload the tgz separately somewhere (anywhere) and let me know where it is and I'll set up the rest.

[phcerdan]

This would be great @get9!