Usage of python list as odml value circumvents dtype checks

[mpsonntag]

Since we removed the odml.Value class and simply replaced it with a python list, this list provides of course methods like append which in turn ignores all the nice dtype checks we would like to have in place to keep odML values consistent.

As an example this currently works w/o any error:

p = odml.Property(name="example", dtype=odml.DType.int, value=[2, 4, 16, 23, 42])
p.value.append("lame ending")