Revert the previous commit that removed 'equals' and 'hashCode' from Matrix3/4 (more investigation has show that it was not a so good idea),
and simplify in an other way by removing 'MatrixSIS.getExtendedElements()'. Instead, we perform that work in GeneralMatrix in a way that put
unconditionally the error terms. Tthis simplify the actual computation by removing a bunch of '(foo == 0) ? foo : foo' operations. This is
more apparent in the Solver class (not yet committed).


git-svn-id: https://svn.apache.org/repos/asf/sis/branches/JDK7@1528555 13f79535-47bb-0310-9956-ffa450edef68