`type` field allows use the array syntax for defining type

[Mingun]

The following .ksy is accepted by compiler (at least in web-IDE) and parses 1 byte:

meta:
  id: type_reference_bugs
types:
  u2be:
    seq:
      - id: value
        size: 1
seq:
  - id: value
    type: u2be[]

I think, that such constructions should be prohibited. The seq.type field should not allow using the "array" syntax for defining a type reference. This not only have unclear semantics, but also threated as a reference to a user type u2be.

Another problem that may be misleading is the ability to have a custom type named as one of the built-in. I think we should prohibit this too. In the example above, if you delete the [] part from the type, built-in type will be used.