big huge changes, so i dont remember everything.

* renaming, e.g. LU ---> FullPivLU
* split tests framework: more robust, e.g. dont generate empty tests if a number is skipped
* make all remaining tests use that splitting, as needed.
* Fix 4x4 inversion (see stable branch)
* Transform::inverse() and geo_transform test : adapt to new inverse() API, it was also trying to instantiate inverse() for 3x4 matrices.
* CMakeLists: more robust regexp to parse the version number
* misc fixes in unit tests

doc/snippets/PartialLU_solve.cpp

@@ -2,6 +2,6 @@ MatrixXd A = MatrixXd::Random(3,3);
 MatrixXd B = MatrixXd::Random(3,2);
 cout << "Here is the invertible matrix A:" << endl << A << endl;
 cout << "Here is the matrix B:" << endl << B << endl;
-MatrixXd X = A.partialLu().solve(B);
+MatrixXd X = A.lu().solve(B);
 cout << "Here is the (unique) solution X to the equation AX=B:" << endl << X << endl;
 cout << "Relative error: " << (A*X-B).norm() / B.norm() << endl;

doc/snippets/Tutorial_solve_multiple_rhs.cpp

@@ -3,7 +3,7 @@ A << 1,2,3,  4,5,6,  7,8,10;
 Matrix<float,3,2> B;
 B << 3,1, 3,1, 4,1;
 Matrix<float,3,2> X;
-X = A.partialLu().solve(B);
+X = A.lu().solve(B);
 cout << "The solution with right-hand side (3,3,4) is:" << endl;
 cout << X.col(0) << endl;
 cout << "The solution with right-hand side (1,1,1) is:" << endl;

doc/snippets/Tutorial_solve_reuse_decomposition.cpp

@@ -1,6 +1,6 @@
 Matrix3f A(3,3);
 A << 1,2,3,  4,5,6,  7,8,10;
-PartialLU<Matrix3f> luOfA(A); // compute LU decomposition of A
+PartialPivLU<Matrix3f> luOfA(A); // compute LU decomposition of A
 Vector3f b;
 b << 3,3,4;
 Vector3f x;

doc/snippets/Tutorial_solve_singular.cpp

@@ -5,5 +5,5 @@ b << 3, 3, 4;
 cout << "Here is the matrix A:" << endl << A << endl;
 cout << "Here is the vector b:" << endl << b << endl;
 Vector3f x;
-x = A.partialLu().solve(b);
+x = A.lu().solve(b);
 cout << "The solution is:" << endl << x << endl;

doc/snippets/class_FullPivLU.cpp

@@ -2,7 +2,7 @@ typedef Matrix<double, 5, 3> Matrix5x3;
 typedef Matrix<double, 5, 5> Matrix5x5;
 Matrix5x3 m = Matrix5x3::Random();
 cout << "Here is the matrix m:" << endl << m << endl;
-Eigen::LU<Matrix5x3> lu(m);
+Eigen::FullPivLU<Matrix5x3> lu(m);
 cout << "Here is, up to permutations, its LU decomposition matrix:"
      << endl << lu.matrixLU() << endl;
 cout << "Here is the L part:" << endl;