[ZF2-412] FilterChain should allow multiple instances of same type
[ZF2-412] FilterChain should allow multiple instances of same type

- FilterChain was also not allowing multiple instances of the same
  filter type.
- Additionally, it was using Stdlib\SplPriorityQueue, which does not
  allow for repeat iteration; altered to use Stdlib\PriorityQueue, which
  resolves that issue.

zf2timo/zend-validator,weierophinney/zend-validator,ezimuel/zend-validator,Maks3w/zend-validator,zendframework/zend-validator,akrabat/zend-validator,svycka/zend-validator