An easier way to create QKAttribute instances

Hey @kylef, how do you feel about this?

Super handy having the KFAttributeFromKey macro, this provides the same for QKAttribute but it's now an inline C function. If you've switched to only having the attributes, etc. auto-generated via your mogenerator script then you probably don't use this. For manually creating QKAttribute's this handy though and should aid in moving from KFAttribute to QKAttribute.