Move parameters that are likely global to global config

[sn0ja]

Some API parameters are set at machine creation, but are very likely to be the same for every machine.
Such parameters should be set globally to make api less complex.
Example: graphics_address in add_linux_domain
Move this from add_linux_domain to the constructor of the Range class.

[sn0ja]

Such parameters (in add_linux_domain) are:

• management_default_gateway
• graphics_passwd
• graphics_address (another option could be to assign it 0.0.0.0 as the default value)
• graphics_auto_port