add requisitions couch view and open_for_location function + tests
temp commit with better support for requisition response processing

- refactor some of the apis to make stock transactions and requisition
  responses able to behave more similarly
- needed to make the requisition responses more aware of other properties
  like domain and location
- pulled out fragment function to the "transaction" classes
actually add support for the bulk requisition workflow

- flesh out the RequisitionCase wrapper and use it in requisition workflows
- explicitly separate Bulk responses from regular ones, let them generate
  regular transactions dynamically
- add support for who requested, approved and filled a req and when
- add a short test and update an existing test
add approval test and add approval to the default requisition options
Merge pull request #911 from dimagi/commtrack-reqs

Support bulk requisition updates like "fill" and "approve"