Merge branch 'release-2.2'

* release-2.2: (71 commits)
  Bump version for 2.2.9-pl release
  Add SDK distribution
  Critical error when resourceTree not initialized (cherry picked from commit 6eda3f1c940fefc99d5cfc6d082ce301855b96a4)
  Avoid suppressed warnings with ob_get_level()
  Update core/lexicon/en/workspace.inc.php
  Bump version for 2.2.8-pl release
  Various documentation corrections
  Fix xPDOIterator->next() using void return value
  Fix undefined constant object in xPDO->toCache()
  Fix xPDO::prepare() sending no driver_options
  Fix xPDO::getInstance() when reusing existing
  Fix invalid call to $this->xpdo->log()
  [#9864] Identify compound PK's properly in xPDOQuery::parseConditions()
  Bump version for 2.2.8-dev
  [#10043] Fix class-loading LFI in registerLogging
  [#6937] Fix Persistent/Reflected XSS in User Messaging
  Optimizing ExtJS Images
  Set default error_handler_types to error_reporting()
  add changelog entry
  [#6294] Remove patch
  ...