Used to generate incremental entity metadata IDs.
pre_meta are local variables, to avoid redundancy.
meta_current_entity is defined elsewhere, and
meta_pre_entity are accessed via it. Those two values are incremented after this template.
Behavior changes if a
meta_prerelease variable is defined: the template supports an optional parameter which may be set to
removed, which can be used to mark metadata entries that were added or removed in the prerelease.