Naming Convention for Type Aliases

[vaibhavhrt]

A consistent naming convention should be used for type aliases.
Maybe CamelCase as the stdlib typing module is in Camel Case, but suggestions are welcome.

Inconsistent names could be found in pandas.io.formatters.formatter, formatters_type and float_format_type. Look for other similar names too and fix them all.

[vaibhavhrt]

I will open a PR after a few days. Meanwhile someone else is welcome to pick it up.

[mroeschke]

Thanks for the request, but it appears this hasn't gain traction in a while so closing