Resolve "Add more good password validators"

Closes #102 (closed)

• I moved "validate" out of the constants file to make it more extendable - as you can see with the same as email validation
• Min length 10 (present state)
• Disallow all numeric
• Require at least 5 unique chars
• Disable email as password

I didn't get "disable email as password" on change password. It's not in the form state so it wasn't trivial to get. I think it's less likely someone would use their email as their password when changing an existing password. I figured this is good enough for now.