Cascade Taxonomy delete

A FK reference on the product_taxon table prevents Taxonomies from being deleted.
This commit adds on-delete=CASCADE to the relationships.
Merge pull request #329 from Richtermeister/fix-taxonomy-cascade-remove

Cascade Delete for Taxonomy and Options
Fix for issue with order processing when given value is not array or Doctrine Collection
Merge pull request #342 from stloyd/bugfix/issue_317

Fix for issue with order processing when given value is not array or Doctrine Collection
Fixed: checkout security return binded form