CRM-12463 QA fix

Fix for the following points:
1. The default values getting jumbled up and getting populated in the wrong autocomplete box of "Select Contact" field each time we refresh the page.
2. Soft credit amount will default to total amount of contribution.
3. If user enters less than total amount of contribution AND adds another soft credit row, the soft credit amount default will be left empty (to allow for "variable splits")