Implement generalized `get` method

[kael-shipman]

Currently the get method is inelegant at best. It first prepares a SQLQuery, then executes the query, sometimes prepares the result, converts the result to jsonapi format, then inflates the result.

It would be nice to organize this method into an Algorithm pattern that utilizes hooks along the way to allow subclasses to alter the results, rather than having to rewrite the method every time.