VlanManager 0.1.2

• Added an option to keep a VLAN from becoming the default route.
• Rejected interface names that are invalid or already used by another interface.
• Rejected host addresses equal to the network address, gateways equal to the address or outside its subnet, and MTU values above the parent interface MTU.
• Showed an error for out-of-range VLAN IDs instead of silently correcting them.
• Kept VLANs whose parent interface is missing visible, so they can be edited or deleted.
• Disabled Add when no managed interface is available and Add/Edit when the 8021q module is missing.
• Translated interface states and the MTU placeholder.