Add character count to captions panel.

When editing captions we need to be able to see the number of characters in a line of a caption to be sure they fit within caption character limits. There is an option to set a character limit when generating captions, but once I start editing captions there is no way to maintain that character limit or see if we have gone over the limit. Please show the character length of each line somewhere in the caption panel. At the very least the info panel could should a character count when a line of text is highlighted.