purge 8.x-3.0-beta8

Actions required after upgrading:

• run drush cache-rebuild to prevent getting any discovery exceptions.

• run drush p-queue-empty to start off with a clean slate (+clean statistics).

• IMPROVED purge_ui's diagnostic report, its colored and visually pretty now.
• APIBREAK Rewrote Queue\StatsTrackerInterface from the ground up.
• APIBREAK Simplified Counter\PersistentCounterInterface and CounterInterface into one merged CounterInterface, and ::setWriteCallback lost its $id parameter.
• NEW TypeUnsupportedException, thrown from InvalidationsService::get(), this prevents people from adding things to their queue that aren't supported.
• NEW QueueSizeDiagnosticCheck which warns after 30000 queue items and does a safety shutdown over 10000.
• NEW and IMPROVED drush commands:
  • cache-rebuild-external (cre): a shorthand for "drush p-invalidate everything".
  • p-processor-add (pradd)
  • p-processor-ls (prols -> prls)
  • p-processor-lsa (prlsa)
  • p-processor-rm (prrm)
  • p-queue-stats (pqs): now has much richer output and a--reset-totals switch.
  • p-queue-empty (pqe): no longer resets statistics (hint: it shouldn't).
  • p-queuer-add (puadd)
  • p-queuer-ls (puls)
  • p-queuer-lsa (pulsa)
  • p-queuer-rm (purm)
  • p-purger-mvu (ppmvu): move a purger UP in the execution order.
  • p-purger-mvd (ppmvd): move a purger DOWN in the execution order.
• FIXED Undefined variable count QueueService:122
• FIXED DatabaseQueue::createItemMultiple() call to db_insert() -> $this->connection->insert()
• FIXED Endless queue-loop of invalidations after removing a purger.

• FIXED drush commands now no longer require a drush cache-rebuild to become visible.