Update acknowledgements and prepare v0.7.0 release

[jank324]

Description

Updates the acknowledgements, adding new authors and funding notices.

Motivation and Context

• I have raised an issue to propose this change (required for new features and bug fixes)

The current acknowledgements do not reflect the work of new contributors who have joined the project. Addresses #267. Closes #165.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Checklist

• I have updated the changelog accordingly (required).
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.
• I have reformatted the code and checked that formatting passes (required).
• I have have fixed all issues found by flake8 (required).
• I have ensured that all pytest tests pass (required).
• I have run pytest on a machine with a CUDA GPU and made sure all tests pass (required).
• I have checked that the documentation builds (required).

Note: We are using a maximum length of 88 characters per line.

[jank324]

@cr-xu, @AnEichler, @Hespe, @RemiLehe, @jp-ga: Please let me know if you have any funding strings or similar that you would like to have mentioned here. If you have nice proposals (e.g. examples from other repositories) for formatting the acknowledgements section, they are also welcome. For now I would list the authors, maybe participating institutions, and provide the funding strings.

[cr-xu]

Just throwing some ideas here, maybe the contributors can be in a bullet list, with trailing links to their GitHub user names (if applicable), for example

• Jan Kaiser (@jank324)

[jp-ga]

This is the funding string from my side:
This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.

[Hespe]

For the current XFEL project, we used

We gratefully acknowledge funding by the EuXFEL R&D project "RP-513: Learning Based Methods"

before.

[jank324]

I've put together what I think is a nice Acknowledgements section now. I know the logos don't render. The absolute paths are on purpose to fix image rendering on PyPI and should fix themselves automatically as soon as this PR is merged onto master.

Let me know if anything is missing. If I don't get any comments, I will merge this as is on Friday before lunch Hamburg time.