Limit results from `razor events`

The list of events in `razor events` can grow unwieldy very quickly. This
change instates a default of all rows returned with options to return
different rows using parameters /api/collections/events:
- `limit` determines the maximum number of rows to return,
which defaults to 20.
- `start` determines what row number to start with, which defaults to 0.

This includes both of these parameters in `/api` under
`collections => events => params`.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-382
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