In poll creation, code, time and date of both creation and end should be automatically set

[MavropaliasG]

The user shouldn't have to set the code (what is this used for??) and also the time and date for creation and end of a poll.

• The code should be automatically set incrementally (make sure we don't have a problem with races)
• Creation time and date should be automatically set as soon as the user presses submit
• Ending time and date should be automatically set to 7 days from the creation date by default