Allow the user to change output textbox font size.

This would make copying the relevant character code/entity easier, especially when going fast with getting the codes/entities to copy into the HTML file. This can be a `NumericUpDown` or `DropDownBox` control and go in a "Formatting" groupbox under a "View & Formatting" or "View + Formatting" tab (I refuse to let everything about Windows Phone and Metro UI die!). Have a preview textbox to show what the font size will look like before saving.

Adding this feature may also require having the Options window use tabs instead of one table layout panel with rows, as there are getting to be several options groupboxes there and too many more will make it too large. Having it be too large with too many options would make it overwhelming.