ENH: add a "name" field to DataFrame, consistent with Series
It would be logical to add a `name` field to DataFrame, similar to Series. Then when you construct a Panel it can try to use the `name`, in the same way as when you construct a DataFrame from Series.

It would also be useful when loading/saving DataFrames to files and DBs, for example at the moment to save to HDF you always have to add a key and for SQL a table name, it would be logical to attach these to the DataFrame itself as its name parameter. 
