User's birth date has no limits

[maciejSamerdak]

We can currently employ children, embryos and time travelers. It's nice that we don't discriminate, but this might be a little overboard and illegal.

Should be done:

• Birth date should be earlier than 18 years ago
• Birth date shouldn't be earlier than at least the beginning of 20th century

[dybi]

closing, as merge failed to close automatically