Implement sign up confirmation

[angristan]

To do

• Prevent SQL injections
• Implement isConfirmed()

[stephane-rbn]

OK. We will have to look at how to setup this confirmation system on my Mac and @LAymeric 's pc. Is ALTER TABLE member ADD confirmation VARCHAR(64); enough to upgrade the database? (accidentally closed the PR, sorry)

[angristan]

@Stephanyan yes it's enough

[angristan]

You'll have to confirm users manually:

UPDATE member set confirmation='1' where username='newuser';