RuntimeMap Save() can cause MgUnclassifiedExceptions on subsequent rendering operations

[jng]

When a RuntimeMap is saved, subsequent rendering operations may throw a MgUnclassifiedException.

This is due to the MgMap deserialization code naively reading in groups as-is and doing parent group assignment on groups that may not have been read yet.

While the true fix is to defer parent group assignment for groups that haven't been deserialized yet, we can add an easy workaround on the RuntimeMap side by forcing the groups to be serialized out in a certain order.

• Groups without parents
• Child groups of the above groups
• Child groups of the above groups
• etc, etc

[jng]

Fixed trunk (r7513) and 4.0.x (r7515)