CRM-15112 - allow dev to not rebuild triggers when creating custom
fields via api.

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* CRM-15112: API create CustomField should expose ability to not rebuild triggers
  https://issues.civicrm.org/jira/browse/CRM-15112
Merge pull request #3836 from jmcclelland/api-trigger-rebuild

CRM-15112 - allow dev to not rebuild triggers when creating custom