Creating compatible ImageData from AcquisitionData and voxels grid dimensions x and y

[evgueni-ovtchinnikov]

Changes in this pull request

Implements an alternative way to create a STIRImageData object from AcquisitionData object suggested by @ashgillman that makes the created image data object compatible with the acquisition data object it is created from.

Testing performed

Related issues

This PR takes over from PR #231.

Checklist before requesting a review

• I have performed a self-review of my code
• I have added docstrings/doxygen in line with the guidance in the developer guide
• I have implemented unit tests that cover any new or modified functionality
• The code builds and runs on my machine
• CHANGES.md has been updated with any functionality change

Contribution Notes

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Please tick the following:

• The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in SIRF (the Work) under the terms and conditions of the Apache-2.0 License.

[KrisThielemans]

@evgueni-ovtchinnikov , please merge master on here for conflicts (probably just in the README). Feel free to squash-merge then (do edit the suggested commit message to remove everything that is irrelevant).