FIXED: Timing issue in destroy of remote pengines
Forgotten newline
ADDED: pengine_create/1: destroy(+Boolean) option (no effect yet)
ADDED: Allow for :- dynamic declarations inside pengines.
TEST: Asking `next` to another pengine cannot work because the `other'
pengine may not have processed its first `ask` yet.
TEST: Add random delays to expose timing errors.
ADDED: Process pengine_create/1 destroy option.
WIP destroy remote message queue and distinguish remote and local pengine
while unregistering.
TEST: Allow using a truely remote pengine server
FIXED: We must destroy the message queue from the HTTP handler when
sending the final destroy event instead of when the pengine terminates.
FIXED: handle destroy/2 events properly in pengine_event_loop/2.
pengine_event/1: handle destroy/2 event as destroy/1.
Added various debugging statements
Make test names unique
TEST: make collect assume destroy(true)
TEST: choose between in-process and external pengine server