Improve error message for missing/invalid study ID

This also includes a stub for delegating PUT actions, in preparation for
normalizing the URLs for our 'push' API methods.
Merge branch 'master' of github.com:OpenTreeOfLife/phylesystem-api
Offer sensible versions of CC-BY (not 4.0)

Addressed in https://github.com/OpenTreeOfLife/opentree/issues/369
Save names for all selectable licenses/waivers.
Merge pull request #100 from OpenTreeOfLife/master

Improved error messages, waiver/license changes to match opentree. This has been tested on devtree and devapi.