Corrections in PortalUser table fields

Corrections in PortalUser table fields:

1. Increase the length of Phone and City DB fields for User prefix.

Currently pone field is 20 characters, while it's 255 for Fax. 255 makes more sense because, for example, 555-555-5555 ext. 555 phone number doesn't fit.

2. Adjust field types and NULL state based on todays rules:

When NULL value has special meaning and it's not the same as empty string
for code using it, then NOT NULL should be used.