Change registration of SpaceGroups into Factory

[Michael Wedel]

The conclusion of a discussion about the growing number of factories in MantidGeometry was that this may lead to longer loading times when Mantid is launched, especially if registering objects requires a considerable amount of work.

• In the case of BraggScattererFactory there are only two registered classes and registering them does not require doing much (it's using Kernel::DynamicFactory).
• For PointGroup, the number of registered objects is small (13) and is ultimately limited to 32. Additionally, PointGroup may change in the not so far future (derive it from the Group-hierarchy, like SpaceGroup).
• SpaceGroupFactory is an issue, because there are hundreds of possible space groups that can be registered and currently a prototype is created when the class is registered - this is computationally expensive in high symmetry cases.

I want to change the way space groups are subscribed to the factory, postponing the creation of the prototype until a concrete group is requested. The first creation of a space group will then be slower compared to now, but a lot of potentially unnecessary work (if space groups are not used) is avoided on launching.

I would like to do this before #10344, where I plan to add many space groups.

[Michael Wedel]

Refs #10504. SpaceGroupFactory now generates prototypes on demand.

Changeset: 4c21f89c631f8b37cce60f5f82b40ff1a2bd2436

[Michael Wedel]

Refs #10504. Extracted prototype generation into method

Changeset: 5f8e2a4f7c231e1df5e9c38dab2f5d92d9b46be4

[Michael Wedel]

Refs #10504. Added AbstractSpaceGroupGenerator and two sub-classes

This will replace a lot of code in SpaceGroupFactory eventually.

Changeset: 49b71ee214143164af07263b5603a3debff00ae3

[Michael Wedel]

Refs #10504. SpaceGroupFactory now uses AbstractSpaceGroupGenerator

The factory now uses AbstractSpaceGroupGenerator-objects to delay prototype construction until it's really needed. Separating the generation out of the factory itself makes it more flexible (other space group generation algorithm) and more focused (factory does not care anymore how prototypes are constructed).

Changeset: 9cdfac7beedc8a30c4baa8dcd2bca654d91a89b9

[Michael Wedel]

Testing information

Code review. Make sure the SpaceGroupFactory system test passes (it has not been modified). The unit test has been expanded a bit - everything that used to work with the old registration method still works with the new method as well. There is also a new test case (using a mock-object) which makes sure that prototype generation is only done once.

[Nick Draper]

Merge remote-tracking branch 'origin/feature/10504_improve_spacegroup_factory_registration'

Full changeset: ​60cbda2ba65c65b6233563b8816984369b45bb3f

[Stuart Campbell]

This ticket has been transferred to github issue ​11346