Fixed DSR discrepancy report bug and a potential date range bug

## Bugs
 - Changed a broken $salesforce->query() call in the discrepancy reports because it was expecting a soql object but we were passing a string. I changed the call to $salesforce->apiCall(...) as is done in other areas of this module.
 - Initialized an orders variable to prevent notices when no orders match the given criteria on a report query.

## Potential Bug
 - Adjusted query date format for drupal queries to use MySQL's from_unixtime() format. This may have caused issues with the boundaries on the date range query but I wasn't able to cause that behavior.

## Extras
 - Added some very basic DSR tests.
 - Removed an unused template file and repaired dsr_theme() and related theme functions.
 - Lots of coder cleanup in the comments.
 - Added some deprecated docblock tags for possible later removal of unused code.
 - Removed an empty file that wasn't included anywhere.

The query here is comparing to from_unixtime(changed), so it wants the matching string dates and not the integer timestamp. Everything that calls this uses string dates, so I updated the documentation.