Rather than having "creation time", "upload time", "registration time"
etc. I think it is better to have a single "creation time"
entity-agnostic property (like the one Tags had thus far).
AbstractSearchService::getByFilter() wasn't injecting lazy loaders,
because it didn't call AbstractDao::afterLoad(). This resulted in tags
not showing up in post list, because there was nothing to retrieve them.
Changed lazy loaders injection so that it's always executed as soon as
possible (i.e. right in EntityConverter).
