bugfix - addes test script for averaging over dimensions and for keeping/removing dimensions from data, fixed some bugs in ft_selectdata_new in the process, see http://bugzilla.fcdonders.nl/show_bug.cgi?id=2508


git-svn-id: svn+ssh://svn.fcdonders.nl/home/svnroot/fieldtrip/trunk@9340 0cf7c7f0-3615-4144-b4e6-68da3bce3cd0