Update DoubleMatrix documentation
Update DoubleMatrix documentation

- Remove misleading comment about not checking the input array in DoubleMatirx(int, int, double...)
- Clarify the copy or view semantics of the various constructors
mpoussevin/jblas,mikiobraun/jblas,mpoussevin/jblas,linux-on-ibm-z/jblas,mikiobraun/jblas,linux-on-ibm-z/jblas,mikiobraun/jblas,linux-on-ibm-z/jblas,mpoussevin/jblas,lipiji/jblas,lipiji/jblas,lipiji/jblas,mikiobraun/jblas