close#2757, refs #5286
- moves error formatting from api/index into errors lib
- moves error handling from api/index into its own middleware
- adds extra middleware for method not allowed which captures all unsupported routes
* refs #5286
* includes test cases for `addClientSecret`
* no tests first `generateAccessToken` and `authenticateClient` because there isn't anything to test in them
refs #5286
- split cache control middleware into its own file
- split out cache control tests
- add new mochacli command for running just middleware tests