Initial files stored before starting testing. Not yet working.

Refs #5591
Working on CubicSpline test class.

Refactored CubicSpline to remove reallocating the spline on every run of the function.

Refs #5591
Added tests for a selection of known and unknown data set points.

Refs #5591
Finished writing unit tests for basic CubicSpline.

Refs #5591
Updated algorithm with a function to calculate derivatives.

Algorithm should now be able to calculate both the first and second derivatives.

Refs #5591
Finishing up derivatives implementation.

Added correction for x points being out of order.

Refs #5591
Fixing exception checking.

Refs #5591
Merge branch 'feature/5591_cubic_spline_algorithms' into develop