Allow spider settings to be set/overridden from `instance/nodes/*NODE*/settings.json`

[iannesbitt]

Related:

• 23

The spider should be able to follow delays and other relevant overrides in a node-specific settings file. For example, Harvard Dataverse wants a 4 second delay between requests, but most other sites can be crawled more rapidly.

[iannesbitt]

Makes more sense as settings.json

[iannesbitt]

Followed suggestion from https://docs.scrapy.org/en/latest/topics/settings.html#settings-per-spider to implement settings changes in Spider.from_crawler()

[iannesbitt]

Tested and working.