BUG: Use id_expression in vtkTypeMacro instead of simple_id.

The id_expression rule allows superclasses to be templates.

Change-Id: I6fdfac6187795467ee81c3a233213c91bc95528f
STYLE: Document an important ambiguity in the parser.

Change-Id: I2dfe2870e14bcef292e7ddb4e55664869a8771a9
Merge topic 'templates-in-typemacro' into master

bc0e62e2 STYLE: Document an important ambiguity in the parser.
cd3aaa27 BUG: Use id_expression in vtkTypeMacro instead of simple_id.