fix typo
Record the collection content type in the StreamerElement and thus on file.

Store in the StreamerElement of the StreamerInfo of a class with a
CollectionProxy the name of the content type.
It stored in the StreamerElement's title at the beginning in the form:

  <ContentType>

We will be able to use this information to recreate a proper collection proxy
in the emulated case.
Start adding protection and error message for customCollection no setup properly.
Prevent TTreeFormula from crashing when requested to access a 'removed' member of a collection
Fix/recreate a collection proxy if it is missing but we have enough info.

For a split collection, the TBranch object actually has the name of the
class contained in the collection.
Recreate a collection proxy if the StreamerInfo has enough information.

Since v5.34/10 and v6, we store in StreamerElement of the StreamerInfo
of a class with a CollectionProxy the name of the content type.
It stored in the StreamerElement's title at the beginning in the form:

  <ContentType>

We can now use this information to recreate a proper collection proxy
in the emulated case.