Option to change colum order without switching to built_in mode

[mattywausb]

Problem; If the order of columns in a repository schema does not align to the necessary concatentation order for the hashkey, you have to switch to built in mode. Further Updates of the schema will be missed or must be synchronized manually (and will remove the customized order). So this can only be a workaround until a better solution.

Solution: Provide an extra property for every column, wich will overrule the schema order. Set this property to a default of "-" (meaning, no sort). The order of concatenation should be: ascending to the order property. Inside the same ordervalue, preserve the schema order, finally add all order "-" columns in order of the schema.