Import preplot file configuration into database.

We do this so that we can look for the "saillineOffset"
parameter, which we expect to be present in source
preplot imports and allows us to correlate source
and sail lines.

The change to bin/sps.py is necessary to let the JSON
serialisation take place.

bin/sps.py

@@ -47,4 +47,5 @@ def from_file(path, spec = None):
 
 			line = fd.readline()
 
+	del spec["normalisers"]
 	return records