IRepository adjustments

[cxallan]

• Removal / deprecation of disk space usage and free functionality that loops through all files in disk
• Addition of new methods for retrieving actual size:

Map<Long, Long> getUserPixelsOnDiskUsage(Parameters p);

// If nothing return empty map
//
// p = omero.sys.ParametersI()
// p.page(offset, PAGE_SIZE)
// p.exp(userId) // mapping to p.details.owner.id comparison
// p.grp(groupId) // mapping to ctx['omero.group']
//
// p.grp() maps to -1 when the user is an administrator and no argument is passed
// p.exp() is not used if it is not provided
//
// Basic code that is being affected by Parameters is:
//
// Map<String, String> ctx = new HashMap<String, String>();
// ctx.put("omero.group", p.grp());
// p.grp(null);
// iQuery.findAllByQuery(
//     "select p from Pixels as p " +
//     "where p.details.owner.id = :experimenter" +  // optional
//     "order by p.pid", p, ctx);
//

Map<Long, Long> getPixelsOnDiskUsage(Set<Long> pixelsIds);