Address dlite-validate output confusing information

[jesper-friis]

Description

If I understood issue #978 correctly, we should not show the warning about the behavior change from dlite-validate. I agree on that.

But how is this solved best? The current implementation expects the user to set environment variable DLITE_BEHAVIOR=OFF to turn off all warnings about behavior changes. If we are happy with that, we are done.

If we want tools like dlite-validate to never show warnings about behavior changes, we need more. Possible approaches:

• Set DLITE_BEHAVIOR=OFF within the tool before importing dlite. This is currently implemented in this PR. It is quite a hack and not a very attractive solution...
• If dlite is imported from Python, it could look for global variables starting with "DLITE_" and set corresponding environment variables internally. I like this better, since it would be a quite general and nice way to configure dlite from Python applications. Now implemented in PR Initialise environment from global Python variables #989

Type of change

• Bug fix & code cleanup
• New feature
• Documentation update
• Test update

Checklist for the reviewer

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?

[jesper-friis]

Closing this PR, since a better solution was implemented in PR #989.