Column placeholder content can't easily be selected and removed #141

When columns are inserted, placeholder content is included. However, it is not simple to remove it. It would be nice if a user could easily click to select the content or perhaps if there weren't even content at all. It would probably be ideal if the content functioned like placeholder content does in input fields where it isn't actual content and placing the cursor in the same place removes the text.

In all honesty, I'm not positive the placeholder content is completely necessary, especially when the column borders are so pronounced.