API Re-factor

[evaneus]

cross cutting issue for some decisions made on API:

• remove elementModels function
• remove register-pie listener and register-pie event (use whenDefined instead)
• remove reset and resetResponse - will move these out to a utility function`reset(sessions):sessions
• rename response-changed to session-changed

Libraries @ version

• pie-player @ 3.0.0
• pie-catalog-client @ 1.0.0
• pie-support-base (merge feature/api-change to master)
• pie-cli @ 8.0.0
• corespring-choice @ ???
• corespring-number-line @ ????
• corespring-placement-ordering @ ???
• corespring-match @ ???
• pie-with-toolbar-demo - try w/ regular custom elements w/ model/session

[edeustace]

need to prove that rm-ing register-pie will be ok