CLN: create core Styler rendering functions and subclass conditional styling applications
Here is a first draft at splitting up `style.py`, ahead of adding new LaTeX functionality

### Key Points

 - All rendering and formatting methods moved to `style_render.py`:

```
class StylerRenderer:
    jinja2_loader
    def render()
    def format()
    def _translate()
    def _compute()

+ their module level helper functions
```

- `style.py` maintains all the conditional application methods and the utility methods and is subclass:

```
class Styler(StylerRenderer):
    ...
```

All methods copied, no changes made, other than deprivatizing shared method names.

Technically this now works:
```
df = pd.DataFrame([['a   b', 'c  v']])
from pandas.io.formats.style_render import StylerRenderer
StylerRenderer(df).format(str.upper).render()
```