Remove LHCb mdf writer compression by default

Remove LHCb MDF writer compression by default, since IOSvc does not currently support compressed inputs and also because there is already compression internally to the "DstData" raw banks (which dominate when no detector raw banks are written out). See #163 (closed). By default, the compression level is currently set to 2.

PyConf/python/PyConf/application.py

@@ -62,11 +62,18 @@ ROOT_KEY = 'ROOT'
 FILE_TYPES = {MDF_KEY, ROOT_KEY}
 
 
-def mdf_writer(path, location, compression=2):
-    """Return an MDF writer which writes a single  TES `location` to `path`."""
+def mdf_writer(path, location, compression=0):
+    """Return an MDF writer which writes a single  TES `location` to `path`.
+
+    By default no compression is used, since `IOSvc` does not currently support
+    compressed inputs and also because there is already compression internally
+    to the "DstData" raw banks (which dominate when no detector raw banks are
+    written out). See https://gitlab.cern.ch/lhcb/LHCb/-/issues/163.
+    """
+
     return LHCb__MDFWriter(
         BankLocation=location,
-        Compress=compression,  # TODO compression ???
+        Compress=compression,
         Connection="file://{}".format(path),
     )