Converts selected tags on GoodReads into rating images (such as tags with half-star ratings).
The rating scale is from 0 to 5 with increments of 0.5
The tag name format is as "rating-TYPE-RATING" where TYPE is "stars" or "clouds" and RATING is "0-0" through "5-0"
Various other tag rating formats are support for convenience ("4-half-stars", "four-and-one-half", etc)
Hyphens are used instead of decimal places for half-star/cloud ratings since the period character (".") is not allowed in tags
Rating images are intentionally not displayed in the add-tag popup area so that it is easier to see auto-complete their text names