AbstractSearch to support use of with by default

[lindyhopchris]

AbstractSearch should have a with method that receives the builder instance. By default, this should apply the contents of $this->with (a new property) if that property is not empty.

The with method should be invoked for both a standard search and a find many search.

This will encourage use of eager loading with searches, which is best practice because of the inefficiencies of not using eager loading when returning multiple JSON API resources at once.

[lindyhopchris]

This feature is now available on Adapter classes on the develop branch and will be released in v0.8.