Text style editors don't properly process new values and raise validation errors

Note: with qt these validation errors are often fatal.

### InstanceEditor

Documentation says that text style editor can be used to modify the trait if the memory address is know, however, the new string isn't processed properly and validation error is thrown:
It's also impossible to recover from this - the error keeps popping up as other editor styles are attempted to use (via `Standard_Editors/InstanceEditor_demo.py`).

### TupleEditor
Similar validation error is thrown with `TupleEditor`, even for very simple type tuples, e.g. `Tuple(Str, Int, Str)`:

### RGBColorEditor

Typing in a valid colour string will set the colour properly, but RGB tuples raise a validation error:

There might be more editors with similar problem. These are the ones I identified by curating demos in `Standard_Editors`