Change default values in the configuration and simplify configuration documentation

[IshaanDesai]

The following defaults are changed:

• Adaptivity metrics output default set to having no output.
• Similarity distance calculation norm default set to L2 relative norm.

Additionally, the default values of configuration parameters are documented in the configuration documentation.

Checklist:

• I added a summary of the changes (compared to the last release) in the CHANGELOG.md.
• If necessary, I made changes to the documentation and/or added new content.
• I will remember to squash-and-merge, providing a useful summary of the changes of this PR.