Create KeyValueParamBase abstract base class

[npetersen2]

If we really wanted to be pedantic, we could make an abstract base class called KeyValueParamBase or the equivalent and put this functionality in it. Then all classes that can be initialized using this method can inherit from this base class.

I rather like this idea since many classes seem to have a copy paste of the createProperties() method. Making it part of an interface would enforce classes to have this capability.

If no one opposes, I'll go and do this change.

[elsevers]

That's a great idea! It follows the 'D' in SOLIDD ('D' for DRY code - 'don't repeat yourself') 👍

[npetersen2]

I'm purposely not going to implement this before the meeting tomorrow, as this will be another reasonably major architecture change.

I would like to resolve some of the PRs into develop first.

At 2019-02-25 meeting, please move this to next week's milestone.

[npetersen2]

Make base class that has createProp() method implemented and abstract method for validateProps(). Also make constructor in base class which calls both of these. The child class should call the parent constructor.

Need to change child properties to public.