Fix syling of long labels in modal

Our forms use a fixed width per default, for nice alignment of multiple
form field. This is not neccessary on single-field preference forms.
Mantis: 3827
Suppress superfluous error messages "Value must be an integer"

and reduce the number of error messages of e164 Subfields, by merging
them into their parent
Mantis: 3723
Consistent naming: Web Username/Password vs CSC Username/Password

Mantis: 3819