[NEST Users] C++ files for synapse models renamed

Dear NEST Developers, With #1972, which I just merged into the master branch, the C++ file names for the synapse models have changed from xyz_connection.h to xyz_synapse.h to make them consistent with the model names we have on the user side. Please pull this change into your branches as soon as possible. This is purely a behind-the-scenes change which does not affect users. Best, Hans Ekkehard -- Prof. Dr. Hans Ekkehard Plesser Head, Department of Data Science Faculty of Science and Technology Norwegian University of Life Sciences PO Box 5003, 1432 Aas, Norway Phone +47 6723 1560 Email hans.ekkehard.plesser@nmbu.no<mailto:hans.ekkehard.plesser@nmbu.no> Home http://arken.nmbu.no/~plesser