Reimplement batch loading

[hbarsnes]

The batch loading from the database has been removed, which makes the loading of many object very slow, which for example impacts the exports for large projects as they are now loading one protein/peptide/psm at the time.

See https://github.com/compomics/compomics-utilities/blob/master/src/main/java/com/compomics/util/db/object/ObjectsDB.java#L507 for the code to be updated.

The solution: re-add the batch loading.