Implemented safer C++ DataContainer data type handling, fixes #1193

[evgueni-ovtchinnikov]

Changes in this pull request

Current C++ DataContainer classes use static casts of void* pointers, which may be unsafe (cf. #1193).

This PR implements an alternative template-based design whereby static casts are only used on C interface level, which is not supposed to be used by SIRF users.

Testing performed

Related issues

Fixes #1193

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

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• 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]

some probably mostly random comments but hopefully helpful in this review.

I'm not sure if templating ImageData is a good idea. It certainly breaks backwards compatibility in a huge way. Possibly this could be done by having an intermediate ImageDataTemplate like you did for DataContainer. However, it might not work, as I guess we'd then need to derive ImageDatafromDataContainer, but ImageDataTemplatefromDataContainerTemplate`. This can be done in C++, but has the potential for some confusion.

[evgueni-ovtchinnikov]

Left unattended for a long time, resulting in weird conflicts with master. Taken over by PR #1210.