outsource reconstruction data in separate arrays

Previously, all fit information data (corresponding key: 'fitinf') from offline files was given to the user in a big chuncked array. To address the issue #16 (closed) 'fitinf data' is restructured into a numpy rec array.

km3io/offline.py

@@ -555,7 +555,7 @@ class OfflineReader:
             empty and does not contain an empty list, then False is written in the
             corresponding index.
         """
-        for i, rs in enumerate(chunk_arr):
+        for i, rs in enumerate(array):
             try:
                 if len(rs)==0:
                     j = None