ZAPD needs more robust error handling

[Kenix3]

In many cases when ZAPD loads a file and the file can't be found, it will just crash. It should output a message like "file not found."

• ZAPD should also support XML file validation per asset type.
• ZAPD should error if an invalid ZResource name is included in the XML.
• ZAPD should error when a ZResource is not in a ZFile.
• ZAPD should error when a ZFile is encountered inside of a ZFile.
• ZAPD should error when a ZResource node has a child.
• ZAPD should error when invalid ZResource attributes and attribute values are provided.
• ZAPD should error if parameters are out of range. For example, a size parameter larger than the type used to store it in ZAPD.

[AngheloAlf]

I have a few questions about this:

• "ZAPD should also support XML file validation per asset type." What does this mean? Does it means ZAPD should check if an the attributes of an asset is valid?
• "ZAPD should error if an invalid ZResource name is included in the XML." I think ZAPD is already checking this here.