Bugfix in GenericIK / DiffIK: When joint space improvement is low, the...

Bugfix in GenericIK / DiffIK: When joint space improvement is low, the iterative search was stopped even when goal was reachable. Now the Cartesian error is considered as stopping condition.

git-svn-id: http://svn.code.sf.net/p/simox/code/trunk@303 042f3d55-54a8-47e9-b7fb-15903f145c44