Resource helpers

[gburgett]

Some additional utility methods on models related to this: https://zube.io/watermarkchurch/development/c/2304 (https://github.com/watermarkchurch/watermarkresources.com/issues/41)

Features:

• resolve now makes use of the Include param added in #47 in order to resolve to the given depth in the most efficient way possible
• A new method resolved? was added to model objects which checks whether links have been resolved to a given depth
• Every model now keeps track of the context that was given when it was found via find or find_by and exposes this on sys.context
• The context exposes a new field sys.context.backlinks which is an array of the parent models from which this model was resolved. Example:

  pry(main)> page = c.main_navigation.items[0].link
  => #<Page:0x00007ff2366e61f0>
  pry(main)> page.sys.context.backlinks
  => [#<MenuButton:0x00007ff22d907de8>, #<Menu:0x00007ff22d3ac218>, #<SiteConfig:0x00007ff23404b388>]

• Model links now expose the ID of the linked entry via #{field.name}_id, similar to ActiveRecord's representation of foreign key columns

Bug Fixes:

• Model implementation auto-loading no longer suppresses NameErrors within the model class defs
• WebhookEnableJob is now only dropped in production
• to_h now returns a hash with string keys, so the resulting hash representation is more similar to json

Documentation:

• Much RDoc, very wow
• Readme.md now includes examples for using the store and client layers of the API via the new Services singleton.
• Convenience methods were added to the CDNAdapter to make it more consistent with other store implementations for the eq query

[gburgett]

The dup code should wipe the ID, since it no longer represents that object in Contentful once it's been duplicated.