Transport: converted to new-style class; Domain: query reduction VirtualMailManager/Transport.py: * added: __slots__ * implemented: __eq__(), __ne__() and __str__() VirtualMailManager/Domain.py (updateTransport()): * reduced db lookups/update

- Aliases
    - avoid looping aliases

- Domain
    - optional limits for number of:
        + accounts
        + aliases
        + destinations/alias
        + alias domains