New TransformHelper<FPP,GPU2> class and misc update in other GPU2 classes.

Add TransformHelper<FPP,GPU2> and quick tests (yet to enhance).
Refactor TransformHelper<FPP,GPU2> and TransformHelper<FPP,Cpu> into parent class TransformHelperGen (yet to finish).
Add Transform::update(), multiply(MatDense<FPP,GPU2>), update get_product, add factor iterator and begin()/end().
Update MatDense<FPP,GPU2>/MatSparse<FPP,GPU2> : move operator overload and ctor, getType.
Update MatDense<FPP,GPU2> tests.
Fix some Vect functions.
Move hpp.in GPU2 files to cpp.in as they are only template specializations (types as variables generated by cmake).

src/faust_linear_operator/faust_TransformHelperGen.hpp

+namespace Faust
+{
+	template<typename FPP, FDevice DEV>
+		TransformHelperGen<FPP,DEV>::TransformHelperGen() : is_transposed(false), is_conjugate(false), is_sliced(false), is_fancy_indexed(false), transform(std::make_shared<Transform<FPP,DEV>>())
+	{
+	}
+
+	template<typename FPP, FDevice DEV>
+		const char TransformHelperGen<FPP,DEV>::isTransposed2char() const
+		{
+			return this->is_transposed?(this->is_conjugate?'H':'T'):'N';
+		}
+}