CRM-14955 - add custom tokens to greetings

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* CRM-14955: can't add custom defined tokens to custom greetings
  https://issues.civicrm.org/jira/browse/CRM-14955
CRM-14948
Merge pull request #3618 from rohankatkar/CRM-14948

CRM-14948
CRM-14871: Rebuild caches after extensions are upgraded in a CiviCRM-managed way (e.g., through the web UI or drush).
CRM-14871: Supply api call extension.upgrade for admins who manage extensions outside of CiviCRM (e.g., manual download).
CRM-14871 - CRM_Extension_Manager - Fix typo
CRM-14871 - CRM_Core_Invoke::rebuildMenuAndCaches - Fix regression where CiviCase XML from newly-downloaded extension doesn't get loaded.
Merge pull request #3619 from totten/master-14871

CRM-14871 - Extension & Flushing
Merge pull request #3616 from jmcclelland/greetings-hook-tokens

CRM-14955 - add custom tokens to greetings