hp-Adaptivity: Smoothness percentage control flexibility

[skvarjun]

User can control the percentage of smoothness values above which p-refinement is favored in hp-adaptivity. For instance, default value is set as 0.9, means p refining favored on an element only if local smoothness is above 90% when compared to the reported smoothness across all other elements.
Important change is that an option argument Real smoothness_threshold = 0.9 is added to base class of select_refinement().

[moosebuild]

Job Coverage, step Generate coverage on 5281dfd wanted to post the following:

Coverage

	a65c5f	#4228 5281df
	Total	Total	+/-	New
Rate	64.54%	63.78%	-0.77%	100.00%
Hits	75858	74956	-902	4
Misses	41673	42575	+902	0

Diff coverage report

Full coverage report

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[roystgnr]

Can we move smoothness_threshold into a member variable of the subclass with an accessor? It's only appropriate in the base class if it's going to be used by every possible subclass, and there are at least some selection possibilities that don't rely on a posteriori smoothness testing.

[skvarjun]

Yes, I agree with this.