Up 3732 tin can api

PR for the TinCan API impl   (https://issues.jasig.org/browse/UP-3718)

- Single on/off switch in properties
- Basic TinCan statement creation
- Basic Auth + OAuth signature authentication support
- Event filtering
- Initial connectivity request via/ activities/states part of the API
- LRS statement submission
- optional batched LRS statement submission
Looks good.  I suggest adding a todo about retrying if it fails but it is expected to work (e.g. is configured) in case the provider happened to be down or temporary network issue when uPortal started up.