Editor for surveys #78 - Fix for vote multiple times #253

[DevPhilB]

Features:

• Surveys with
  • a title
  • multiple questions with small text input
  • multiple questions with large text area
  • multiple questions with single-/multiple choice(s)
• can be created (questions can also be deleted at any index)
• Validation of title, questions and choices
• API for surveys (create, get=entries/results, update=submit)

Fixes:

• User can vote multiple times if they press F5 or reload the board (#253 )

To check if post & survey was created use the following SQL statement: SELECT * FROM "post" WHERE type_of_post = 'application/survey'; SELECT * FROM "survey" LIMIT 1000;

[DevPhilB]

Closed this PR in favor of #268. Reasons:

• Visual feedback after creating a survey was requested (@Simon-Deuring - Point 4)
• feature/display-surveys-21 is already well advanced and includes all commits from feature/post-surveys-78