C++: Remove Templating from Libs/Optimize

[HeavenlyBerserker]

Templating is not used, so it should be removed to facilitate new functions and classes.
Alan: Trying to change anything causes issues for other people who work on Libs/Optimize when merging.

(long term goal)

[sheryjoe]

@akenmorris @HeavenlyBerserker Is this planned for the next release?

[akenmorris]

No, it's a long term goal. We're part way there. I wouldn't tie it to any release as it does not affect users or the computation. It will speed development when done though.

[akenmorris]

Getting there. Have removed lots of the useless templates.

[HeavenlyBerserker]

Remaining templates are in

• Container/GenericContainer and inherited classes
• Domain/ImageDomain and inherited classes
• Domain/VtkMeshWrapper
• Neighborhood/PowerOfTwoPointTree
• Utils/ObjectReader and Writer
• Utils/ParticleGaussianModeWriter

Not all of them need to have templates removed, I think. I'm looking into Domain/VtkMeshWrapper through issue #1408.