Document Validation doesn't check for undefined types

[dgovil]

In our test suite we were seeing that the Document Validate Method doesn't validate types on input parameters as being defined.

For example we have some versions of matrix adds that use 2x2 mats like so

  <nodedef name="ND_add_matrix22" node="add" nodegroup="math">
    <input name="in1" type="matrix22" value="1.0,0.0, 0.0,0.0" />
    <input name="in2" type="matrix22" value="0.0,0.0, 0.0,0.0" />
    <output name="out" type="matrix22" defaultinput="in1" />
  </nodedef>

This passes validation even though there is no typedef for matrix22. We do have our own separate validation suite that catches this, but I think it would be great if we can have the validate method also validate types as well. It would also help catch typos and the like.