CRM-15387 - Add legacy support for honor_contact_id in contribution create api, fix legacy support for soft_credit_to so that soft_credit_type is set to default. Add tests for both.

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* CRM-15387:
  https://issues.civicrm.org/jira/browse/CRM-15387
Merge pull request #4266 from davecivicrm/CRM-15387a

CRM-15387 - Add legacy support for honor_contact_id in contribution crea...