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/FullPivLU_solve.cpp

@@ -0,0 +1,11 @@
+Matrix<float,2,3> m = Matrix<float,2,3>::Random();
+Matrix2f y = Matrix2f::Random();
+cout << "Here is the matrix m:" << endl << m << endl;
+cout << "Here is the matrix y:" << endl << y << endl;
+Matrix<float,3,2> x = m.lu().solve(y);
+if((m*x).isApprox(y))
+{
+  cout << "Here is a solution x to the equation mx=y:" << endl << x << endl;
+}
+else
+  cout << "The equation mx=y does not have any solution." << endl;