Added a default configuration

[ricardogsilva]

Overview

This PR adds a default configuration to pygeoapi, making it optional that the user supplies a config file location. pygeoapi is able to run with this default config. Moreover, as discussed in #1512, it also allows user to supply a partial configuration, which is then merged with the default config.

Related issue / discussion

• fixes Provide a default configuration if none given #1512

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[github-actions]

This Pull Request has been inactive for 90 days. As per RFC4, in order to manage maintenance burden, it will be automatically closed in 7 days.

[github-actions]

As per RFC4, this Pull Request has been closed due to there being no activity for more than 90 days.