CRM-13786 Applying updated patch from Karin which fixes the calculation of start date and edndate  for fixed memberships. All related BAO, api and Form unit tests passing now.

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* CRM-13786: Membership End Date not calculated properly for fixed period MembershipTypes
  http://issues.civicrm.org/jira/browse/CRM-13786
Merge pull request #2059 from davecivicrm/CRM-13786b

CRM-13786 Applying updated patch from Karin which fixes the calculation ...