flush out the unit tests for `(process-revision-event ...)` function which handles new events related to revision tracking.

create an `:mb-run-mode` config property which defaults to "prod" and add couple predicate functions in our config ns for checking `is-prod?` and `is-test?`.  then update our event listener startup calls and wrap them with `(when (config/is-prod?) ...)` so that we only start them up when we intend to run the app for real.  lastly, update our environment for our expectations unit tests so that :mb-run-mode is "test" and thus our event processing listeners are not started for unit tests.

quick tweak to revision code to avoid protocol implementations on classes as basic as java.lang.Object so that functions like `satisfies?` can be useful.  this simply removes the base implementation of IRevisioned from java.lang.Object and instead defines a couple default implementations of the protocol functions which entities can reuse.  also, we remove the base implementation of `serialize-instance` because that just feels dangerous and we want to encourage each entity to provide its own version of that function.

upgrade the revisions code to work off our new events system so that we can remove some unnecessary code from our api endpoint implementations.

also, included here is a small tweak to the revision model to add a new field/column for :is_creation which is true when we know the revision represents the time when the object was created.

another attempt to fix activity api unit test.

Activity feed bug fixes

a couple small tweaks to our activity unit tests to prevent race conditions which intermittently cause test failures.

API Cleanup

title attribute for add question. fixes #964

New homepage implementation with Activity Feed + Recently Viewed