Merge pull request #192 in ZP/z-push from feature/ZP-698-Allow-different-IPC-backends-using-current-IPC-logic to develop

* commit '2bb112bd':
  ZP-698 Renamed getIsDownTime() to getIsDownUntil().
  ZP-698 Fixed name as it was wrong in the correction comments.
  ZP-698 Another dot in a class that shouldn't need to be touched.
  ZP-698 added a dot before someone gets crazy and writes another 64 comments about it.
  ZP-698 fixed typo in memcached provider filename, when waiting for a mutex only log up to 5 messages (spread over the configured total amount of time), if memcache is down don't retry in other connections for up to 30 seconds (configurable), removed TCP_NODELAY and NO_BLOCK options, memcache servers are setup in a single string, renamed ReInitSharedMem() to ReInitIPC(), fixed comments and public/private/protected visibility, fixed upper/lowercasing of method names, added some dots.
  ZP-698 Remove debug.
  ZP-698 Renamed IPC backend to IPC Provider, added general config section, added config file for memcache provider, InterProcessData autoloads available IPC providers.
  ZP-698 Allow different IPC backends using current IPC logic. Released under the Affero GNU General Public License (AGPL) version 3. adding a Memcached backend and - by default disabled - configuration in config.php
  ZP-698 Allow different IPC backends using current IPC logic. Released under the Affero GNU General Public License (AGPL) version 3. split up into a backend interface, a SHM backend and abstract class
  ZP-698 Allow different IPC backends using current IPC logic. Released under the Affero GNU General Public License (AGPL) version 3.