Report errors when trying to using optional ranges

[VeaaC]

@range attribute cannot be combined with @optional: Users should store empty ranges instead (see #249).

This change make sure to report an error

14:30:42 - CRITICAL - app:71 - Error reading schema: @range cannot be combined with @optional, store empty ranges instead: edges_range 

For this schema:

namespace foo{
const u32 NO_EDGES_REF = 200;
struct Node {
    @range(edges_range)
    @optional( NO_EDGES_REF )
    first_edge_ref : u32;
}
}