fix error on display poll
Task #5422 delete/validate choice, only owner can add choice
Task #5464 Create ViewLink Behavior and attach it to models
Merge pull request #64 from VanGiang/task/5422

Task #5422 delete/validate choice, only owner can add choice
Merge pull request #63 from wataridori/task/5464

Task #5464 Create ViewLink Behavior and attach it to models
Merge pull request #60 from thaipt1012/task#5462

fix error on display poll
fix delete all poll and comment when delete user