Correct/improve dragbox docs
Remove transient jsdoc dependencies

alpha9 has the dependencies fixed again, so no need to keep taffydb and
underscore around.
Make sure that projection is an ol.proj.Projection instance
Merge pull request #2321 from ahocevar/cleanup-package-json

Remove transient jsdoc dependencies
Merge pull request #2322 from ahocevar/view-projection

Make sure that projection is an ol.proj.Projection instance
Merge pull request #2204 from probins/dragbox

Correct/improve dragbox docs