Fix for issue #651: Crash when there is only one datapoint in a dataset

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/retistruct@1281 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Fix for Issue #649:
Error message: the condition has length > 1

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/retistruct@1282 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Fix for Issue #652: Faulty export of wedge coordinates to matlab

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/retistruct@1283 edb9625f-4e0d-4859-8d74-9fd3b1da38cb