Add ability to add additional express middleware

[chrisdmacrae]

The ability to add express middleware in a project or template would be ideal.

Some use cases:

• To connect to an database/third-party to add data to the prototype dynamically
• To add different authentication methods
• To add different data file supports?

[chrisdmacrae]

Need to consider building an API execution pipeline so that people understand where and when the middleware will be executed...