Fixes problem when iterating over CSV data with foreach()

The last line was always missing because foreach() uses valid() and then next() to determine if the end is reached
Implements upload and import of coupon codes in ExtJS controller
Adds import button for uploading codes in coupon code panel
Optimizes retrieving configuration values and fixes @since tags
Improves data type handling
Merge pull request #730 from nsendetzky/master

Implements upload and import of coupon codes