Submit form security: #2 back-end

[AnnaigJegourel]

• [x] Create checkArray() in MainController to check if fields are empty
• [x] Create checkArrayElement() in MainController to check if value is in database

Parse input type & use checkArray (+add error message if necessary) in controllers for demanded forms:

• [x] create comment
• [x] create post
• [x] update post
• [x] contact/mailer

Parse input type & use checkArray (+add error message if necessary) in controllers for other forms (user methods):

• [x] create user
• [x] update user
• [x] update password