Add low-level method to find the best UB matrix given 3 or more indexed peaks.

[Dennis Mikkelson]

When 3 or more peaks have been indexed by some method, a corresponding UB matrix can be determined. If more than three peaks have been indexed, the problem of finding the corresponding UB matrix is over-determined. A least squares solution for UB can be efficiently and accurately found in this case, using QR factorization of the matrix with (h,k,l) values as rows. This method will provide a useful component for several other indexing methods.

[Dennis Mikkelson]

(In [12553]) Added support class with method to find the best fitting UB matrix, given a list of q-vectors and corresponding hkl-vectors. refs #3178

[Dennis Mikkelson]

(In [12567]) Added error checking. Now throws exceptions if the UB matrix can't be found from the specified hkl and Q vectors. refs #3178

[Dennis Mikkelson]

(In [12583]) Minor changes to conform to Mantid style. Moved method documentation from .h to .cpp file. Added GPL to header file. refs #3178

[Dennis Mikkelson]

(In [12659]) Added method to count the number of peaks that are indexed to within a specified tolerance by a given UB matrix. refs #3178

[Dennis Mikkelson]

(In [12660]) Fixing problems due to moving Matrix and V3D to Kernel. refs #3178

[Andrei Savici]

At least calculating the UB matrix is correct, or has teh same mistakes that I have in a different program :)

[Stuart Campbell]

This ticket has been transferred to github issue ​4025