Fixed CRM-14545. "Contribution Amounts Label" is respected even when used for memberships.

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* CRM-14545: Contribution page does not respect "Contribution Amounts Label" when page is also used for memberships
  https://issues.civicrm.org/jira/browse/CRM-14545
Merge pull request #2999 from GinkgoFJG/CRM-14545

Fixed CRM-14545. "Contribution Amounts Label" is respected even when used for memberships.