Reorganized module import.
Dropped the import of constants.VERSION, when it wasn't really needed.
Centralized the import of os, re and locale in VirtualMailManager/__init__.py.
Also moved w_std() and w_err() from vmm to the __init__.py.
- Aliases
    - avoid looping aliases
- Domain
    - optional limits for number of:
        + accounts
        + aliases
        + destinations/alias
        + alias domains