SwanSpecFile.__init__() fails reading locations from header when location names are present

[dpzimmer]

Often SWAN 2D ASCII spectra may contain location names present in the coordinate definition section of the header.

See https://swanmodel.sourceforge.io/online_doc/swanuse/node50.html

"Note that if the file is used for input for SWAN (but not generated by SWAN) and the user so desires, the names of locations can be written behind the two coordinates; these names are ignored by SWAN when reading the file (see remark on format above)."

To allow for this, a fix such as below is required to swan.py:

            for ip in locs:
                # xy = [float(val) for val in ip.split()]
                # self.x.append(xy[0])
                # self.y.append(xy[1])
                xy = ip.split()
                self.x.append(float(xy[0]))
                self.y.append(float(xy[1]))

[rafa-guedes]

Thank you @dpzimmer, we would welcome some pull request on this!