CRM-20224 - Civi\API\Events - Rename internal events (`api.foo` vs `civi.api.foo`)

CRM-20224 - Civi\API\Events - Rename internal events (`api.foo` vs `civi.api.foo`)

If you look at the list of events emitted through the EventDispatcher, you'll
find several different formats for the names:

```
   actionSchedule.getMappings
   actionSchedule.prepareMailingQuery
   api.authorize
   api.exception
   api.prepare
   api.resolve
   api.respond
   civi.core.install
   civi.token.eval
   civi.token.list
   civi.token.render
   DAO::post-delete
   DAO::post-insert
   DAO::post-update
   hook_civicrm_caseChange
   hook_civicrm_post::Activity
   hook_civicrm_post::Case
   hook_civicrm_unhandled_exception
```

This patch renames events using the `api.foo` convention.  Based on
grepping universe, I don't believe any extensions rely on the `DAO::*`
events.