Sync activity updating

This PR presumes that others have already been merged [#51](https://github.com/ets-berkeley-edu/datacultures/pull/51), [#55] (https://github.com/ets-berkeley-edu/datacultures/pull/55), and [#59](https://github.com/ets-berkeley-edu/datacultures/pull/59).  That code has been merged into the local branch before developing.

https://jira.ets.berkeley.edu/jira/browse/CYB-122

* Caches student activity scores
* only updates when Canvas is polled
  * All actions are scored at once (internal DataCultures actions do not score sooner)