neuron: CoreNeuron can read rebalanced files.dat. Use a sentinel value

Author: ferdonline

bluebrain/repo-patches/packages/neuron/package.py

@@ -14,6 +14,7 @@ class Neuron(BuiltinNeuron):
 
     # BBP specific version
     version("develop", branch="master")
+    version("9.0.a18", commit="d0f0cfe")
     version("9.0.a17", commit="c48d7d5")
     version("9.0.a16", commit="13654b3")
     version("9.0.a15", commit="f64b609")