Make StorageSerializer a template class

Make StorageSerializer a template class

This patch modifies StorageSerializer so that it will be able to use
other streams than std::ostream and its derivatives. Within current
class hierarchy custom output streams with overloaded insertion operator
(operator<<) cannot be used, as it is non-virtual in std::ostream.

Change-Id: I3e713329c55aacfbb8daa23a5c4579d4c5db9f52