Add ability to configure empty file behavior in IOs

This is a general feature request based on frequent questions I see on Stack Overflow. I often see questions about how to get an empty file instead of no file when a PCollection is empty, or vice versa for IOs that create empty files. In other words, whichever approach is taken, there's users that will want the opposite approach.

It seems the best approach here would be to add some kind of common code (FileIO maybe?) that could either open files for writing in Setup or lazily in ProcessElements.

Regardless of the approach taken, this bug is basically for investigating this feature for feasibility and maybe holding sub-tasks/blocking bugs for tracking implementation.