Make anonymiser more strict about the translation of values

the anonymiser replaces letter and number characters in string values during xml backup. A more strict anonymiser would replace more characters. For passwords in particular (i.e. mail server passwords) this could increase security by translating all characters except whitespace. Whitespace should be preserved to ensure a similar page layout.

We should anonymise hostname, username and password fields by replacing all characters while leaving the current practice for the others.