Made the exported types editable and also the admin screen friendlier with displaying label instead of machine type.

while the previous performance check was totally misguided -- if you dont want the block, don't enable it -- but there is no point in cutting performance if you can't access the block. also capture usernames.

naught101: use hook access to stop blocks displaying if user doesn't have relation creation permissions

Uninstall should delete the endpoints field to allow removal of the field_endpoints module. Fixes #1303016

Issue #1294134 by naught101: Fixed Warning: Missing argument 1 for relation_get_available_types(), general relation_add refactor.

naught101: Remove dummy field widget after discussion with chx. If someone else comes up with a good one in contrib, we can potentially include that.

Issue #1290656 by boombatower: Fixed relation_load() and relation_load_multiple() do not pass  along.

Issue #1233448 by clemens.tolboom: Fixed Error on admin/structure/relation/generate when no relation types defined yet.