Refactoring header style code in TableView

Same or similar code is present in `table_view.TableView` create a function to avoid repetitions.

* `render_header()`

```python
class_name = getattr(self.model, elem).__class__.__name__
if elem in self.style_header and class_name == 'TextField':
# atm header style con be applied only to TextField
# type. ( and class_name == 'TextField )

style_name = self.style_header[elem]['style']
commands = self.style_header[elem]['commands']
my_style = Styles.style(style=style_name,
commands=commands)

new_row.append(getattr(self.model,
elem).render(style=my_style))
else:
new_row.append(getattr(self.model, elem).render())
```

* `render_inner_table()`

```python
class_name = getattr(self.model, elem).__class__.__name__
if elem in self.style_header and class_name == 'TextField':
# atm header style con be applied only to TextField
# type. ( and class_name == 'TextField )
style_name = self.style_header[elem]['style']
commands = self.style_header[elem]['commands']
my_style = Styles.style(style=style_name,
commands=commands)

compliant_data[sr][sc] = getattr(self.model, elem).render(style=my_style)
else:
compliant_data[sr][sc] = getattr(self.model, elem).render()

```

Start at table_view.TableView and compare render_header() with render_inner_table(), using the repeated style and render logic shown in the issue as the scope. Extract the shared behavior so both methods use it while preserving their existing outputs; done means the duplication is removed without changing header or inner-table rendering.

Written by the indexing model from the issue text.