Adding unnamed DataFrames to EntitySets (and have Featuretools generate a name for df)

### Adding unnamed DataFrames to EntitySets

-----

#### Bug/Feature Request Description

Currently, in EvalML's [DFSTransformer](https://github.com/alteryx/evalml/blob/main/evalml/pipelines/components/transformers/preprocessing/featuretools.py), we run into issues with un-named dataframes being passed to the DFSTransfomer's .fit() method.

Calling the DFSTransformer.fit() results in the dataframe being added to an EntitySet() via the _make_entity_set() method which uses FT 1.0.0's new add_dataframe() method. add_dataframe() now requires either:
1.) a dataframe that is not woodwork initialized, whereupon it initializes it and names it according to a parameter passed in via add_dataframe()
2.) a dataframe that is woodwork initialized and named.

EvalML currently supports woodwork initialized dataframes that are unnamed.

#### Expected Output

We'd suggest the following changes:

```
if dataframe.ww.schema is None:
...

else:
if dataframe.ww.name is None:
if dataframe_name is None:
raise ValueError('Cannot add a Woodwork DataFrame to EntitySet without a name or a proposed name')
else:
dataframe.ww.name = dataframe_name
if dataframe.ww.index is None:
if index is None or not make_index:
raise ValueError('Cannot add Woodwork DataFrame to EntitySet without index')
else:
# do index stuff
```
Hopefully we could do something similar to accommodate woodwork initialized dataframes and just give them a name, per the add_dataframe() function.

#### Output of ``featuretools.show_info()``

Featuretools version: 1.0.0