Add option to write inactive equations and terms

[geofjamg]

Signed-off-by: Geoffroy Jamgotchian geoffroy.jamgotchian@gmail.com

Please check if the PR fulfills these requirements (please use '[x]' to check the checkboxes, or submit the PR and then click the checkboxes)

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem ? If so, link to this issue using '#XXX' and skip the rest
No

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
feature

What is the current behavior? (You can also link to an open issue here)
There is no way to write an equation system and see inactive equations ands terms.

What is the new behavior (if this is a feature change)?
An option has been added to write into [ ] inactive equations and terms.

Does this PR introduce a breaking change or deprecate an API? If yes, check the following:

• The Breaking Change or Deprecated label has been added
• The migration guide has been updated in the github wiki (What changes might users need to make in their application due to this PR?)

Other information:

(if any of the questions/checkboxes don't apply, please delete them entirely)

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

94.3% Coverage
0.0% Duplication