Remove leftover ACL code from release/v1.0 branch

[martinmr]

Earlier @MichelDiz was helping a user with #3529. On of the issues is that when exporting from an instance running 1.0.x, the ACL predicates are exported. Since those predicates have changed definitions since they were introduced, an error will occur if someone tries to import that schema into a new version (>= 1.1).

It's not the first time some issue happens because there's ACL code in the release/v1.0 branch but the feature is not complete. I think it's best to remove the ACL code from that branch to avoid future confusion and bugs.

Assigning to @gitlw since he wrote the feature and probably knows best how to do this cleanup.