Fixed support for actor methods
Fixed support for actor methods

- Removed remaining support for hard-coded method APIs
- Added hook to server_method() to execute actor methods

Example: zbroker/zpipes_server, "JOIN CLUSTER" and "LEAVE CLUSTER"
methods.

bkmit/zproto,vyskocilm/zproto,hintjens/zproto,jdiez17/zproto,hintjens/zproto,jemc/zproto,jemc/zproto,c-rack/zproto,zeromq/zproto,jemc/zproto,asokoloski/zproto,sappo/zproto,jdiez17/zproto,bkmit/zproto,zeromq/zproto,sphaero/zproto,sappo/zproto,vyskocilm/zproto,somdoron/zproto,vyskocilm/zproto,jdiez17/zproto,zeromq/zproto,hintjens/zproto,vyskocilm/zproto,hintjens/zproto,vyskocilm/zproto,c-rack/zproto,jdiez17/zproto,sappo/zproto,sappo/zproto,bkmit/zproto,c-rack/zproto,bkmit/zproto,sappo/zproto,asokoloski/zproto,zeromq/zproto,c-rack/zproto,somdoron/zproto,sphaero/zproto,sphaero/zproto,somdoron/zproto,jdiez17/zproto,hintjens/zproto,asokoloski/zproto,zeromq/zproto,asokoloski/zproto,hintjens/zproto,vyskocilm/zproto,somdoron/zproto,bkmit/zproto,jemc/zproto,sphaero/zproto,hintjens/zproto,somdoron/zproto,c-rack/zproto,sappo/zproto,somdoron/zproto,jemc/zproto,asokoloski/zproto,jdiez17/zproto,sphaero/zproto,asokoloski/zproto,jemc/zproto,sphaero/zproto,jemc/zproto,zeromq/zproto,c-rack/zproto,somdoron/zproto,asokoloski/zproto,jdiez17/zproto,c-rack/zproto,sappo/zproto,bkmit/zproto,vyskocilm/zproto,zeromq/zproto,bkmit/zproto