Adjoint operator

[epapoutsellis]

Describe your changes

Added a new adjoint operator in CIL and fixed some errors with the complex matrix operator.

Describe any testing you have performed

Please add any demo scripts to CIL-Demos/misc/

Link relevant issues

Closes #1643

Checklist when you are ready to request a review

• I have performed a self-review of my code
• I have added docstrings in line with the guidance in the developer guide
• I have implemented unit tests that cover any new or modified functionality
• CHANGELOG.md has been updated with any functionality change
• Request review from all relevant developers
• Change pull request label to 'Waiting for review'

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

• The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License.
• I confirm that the contribution does not violate any intellectual property rights of third parties

[MargaretDuff]

This is currently on hold due to the issues with the complex matrix operator in #1646 and #1647

[MargaretDuff]

Thanks @epapoutsellis for this work! Just a few minor comments but looks like a good addition and a good fix

[MargaretDuff]

Also, closes #1646 closes #1647

[MargaretDuff]

A good addition of the Adjoint operator - requested by @jakobsj

Also a fix to our matrix operator adjoint

Also a fix to allocate to work with complex datatypes

[hrobarts]

This is looking good to me! I just had a couple of questions

[jakobsj]

Looks good to me, just some tiny editorial comments. No need to see the PR again after fixing.

[MargaretDuff]

Jenkins is happy