New Inspector control: "Reset to Style" for text elements

Ubuntu 14.04, GIT commit: 4eda1f6

See discussion in #24436: Changes made in Text Properties do not affect all selected elements for background. Bottom line is, a way to reset a group of selected text items to the style defaults is needed, especially to handle 1.3 scores in which this case will arise pretty often. It seems the button in Text Properties wouldnt work for this even Text Properties worked for multiple items, for reasons discussed in that issue (no callback, unclear behavior if elements of different text types selected).

I think this is worth considering for 2.0, although of course I realize that means it needs to be implemented ASAP. I'm willng to do it if we can agree it is the worth adding.