Switch to JsDuck for documentation

There is a Jenkins job for JSDuck which would be useful to make use
of to ensure we write more documentation.

The documentation generated by JSDuck is also far superior

Note this currently gives warnings due to documented non-classes
(we can resolve this latter)

Change-Id: Ic4437c6328dbcb0485e0620fad3020df437e4d97
Merge "Switch to JsDuck for documentation"