Limit events returned from `/api/collections/nodes/:name/log`

In addition to `/api/collections/events`, the view for the node's
log also needs to be filtered. This will allow the same parameters
('limit' and 'start') to be passed in order to filter the returned
collection.

The result from `/api/collections/nodes/:name` will have a key
for `params` which will indicate that `limit` and `start` are
both valid for the `log` collection.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-368