Following our last OCDB design meeting I've modified the Grid CDB access

Following our last OCDB design meeting I've modified the Grid CDB access
classes, adding a dummy subVersion number in the file name. In this way
one can copy a Grid folder locally and read it with the local CDB access.

I've ensured backward compatibility: AliCDBGrid can read also files with
the old name format. New files are nevertheless stored in the new format.
Thus at some point we may think to remove the backward compatibility.

I also send you an updated version of AliCDBManager, where I've added the
"UnloadFromCache(const char* path)" method. This can be used to delete
from the cache a single object, while ClearCache removes them all. It may
be useful if we want to implement the idea of loading and unloading
the calibration data during reconstruction...

Alberto