[WIP] Excel table output
- [x] closes #24862
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

This PR should allow writing excel table objects. Proof of concept implemented for XlsxWriter and OpenPyXL. Exactly which options of the `to_excel` api should be supported is up for discussion, see #24862.
 
```python
import pandas as pd
data = {'B' : dict(col1=1), 'A' : dict(col1=2), 'C' :dict(col1=3, col2=4.1)}
df = pd.DataFrame.from_dict(data, orient='index')

df.to_excel('test1.xlsx', engine='xlsxwriter', as_table=True, index=True)
df.to_excel('test2.xlsx', engine='openpyxl', as_table=True, index=False)
```

