New Engines and Cleanup of Old Ones

Ben

The following engines have been added:
Pixabay: Royalty-free media repository.
OpenAlex: Repository of scientific papers, authors, and institutions.

In addition, the following defunct and unsupported engines have been removed:
Yummly
Searchcode

Additional notes:
The Wordnik engine, which was previously a dictionary, has been converted to an answerer.