Implementing the possibility of loading the CDB as a snapshot in two ways:

Implementing the possibility of loading the CDB as a snapshot in two ways:
1) you suppose you have it locally, in ./OCDB. That will be the case if you untar a CDB tarball.
2) you suppose you can find in some place in alien a root file containing both a map of the
   CDB entries and a list of the corresponding Ids (for the UserInfo)

1) is triggered by using:
cdb->SetDefaultStorage("snapshot://*) where one would put instead of "*" the original alien
location from where the tarball has been built.

2) is triggered by the call:
reco->SetFromCDBSnapshot(filename)
where filename is the name of the file containing the entries map and the ids
list.

1) is implemented in AliCDBLocal and AliCDBLocalParam changes
2) is implemented in AliReconstruction and AliCDBManager changes. For 2) also
the macro macros/MakeCDBSnapshot.C is added, as an example of how to produce
the snapshot file.

Additionally two coding conventions fixed in AliCDBManager (adding const to two parameters).