Updated all password validation to use central password defaults
system while updating length requirements to now all match
at 8 characters minimum.
Some language text was technically correct (More than 7 characters)
but this has been updated for clarity and to prompt other translations
to be updated.
Closes#2237
Still uses gravatar as a default.
Updated URL placeholders to follow LDAP format.
Potential breaking config change: `GRAVATAR=false` replaced by `AVATAR_URL=false`
Builds upon #1111