For using UnitCell in PropertyWithValue, it would be necessary to change the stream operator of UnitCell,
because that is only used for printing at the moment and the precision is limited to 1e-3, which is not enough
for cases like powder diffraction (for example at POLDI, where lattice parameters are determined with precision
better than 1e-4).

Instead of modifying the interface of UnitCell I chose to add explicit string conversion functions. It should be
straightforward to change later on.

This is being done to centralize the code for printing out lattice
constants and their uncertainties.

Though couple of additional unit tests will be useful.

It is now forward declared and the dangerous using
Mantid::Geometry::OrientedLattice has also been removed.

Refs #3515: Sample saving to NXS complete except SampleEnvironment. Refs #3669: Some code testing XML saving/parsing.

Refs #3175. Sorry for the huge commit but certain things require Matrix to be in Kernel. Given how Quat, V3D and Matrix inter cooperate it seemed sensible for them to be in the same place and arguably this is where they belong anyway.

Refs #3175. Add a MatrixProperty that will allow Geometry::Matrix objects to be passed into algorithms. Also renamed the MantidMat typedef to DblMatrix so that it's clearer what the thing actually is.

Refs #3157 Sort our System.h. It was becoming a dumping ground. It should only be touched when absolutely necessary as it affects every file in Mantid. Also combined this with Refs #2345 to sort out DLLExport/DLLImport usage. It's done for Kernel, Geometry and API but stuff in the plugins could do with updating as well.

Refs #3073: Quick adding OrientedLattice to Sample object. Much more painful fixing of MDGeometry stuff to use OrientedLattice instead of UnitCell.

Refs #2841: Added some utility methods to UnitCell. Used UnitCell in PredictPeaks to find HKL range.

Unit cell modified to have method, which returns the rotation, needed for MDGeometry; Tests for UnitCell modified accordingly. 

MDGeometry basis modified to be orthogonal
Unit cell modified to have method, which returns the rotation needed; All operations with this rotation are not fully tested yet. 

Seems like some builds fail since I included UnitCell in geometry. It was already defined in MDGeometryBasis.h. Refs #829.