Revert "Implemented G/g number formatting"

This reverts commit 39259b07fc0b1fd08e496e72f2dd8521f151a459.

Apparently I didn't check this commit thoroughly enough, and it has (at least) the following problems:

1. (0).ToString() returns an empty string (the biggest problem), and
2. I don't like the extra argument to netFormatNumber. I think we should always use the default of 15 (and trim trailing zeroes).