eBay hide duplicate results updated

easy toggle to show or hide bunches of repeated results in eBay searches

v1.4 24/04/2017 Implemented UI and internal changes necessary to allow the user to change the similarity threshold; the value is saved using GM_setValue. Made the selection of candidate items for hiding slightly more intelligent so that it should coexist even better with other scripts that also hide items. Removed support for old style pages. Changed includes to use tld as requested by Mikhoul.
v1.1 13/03/2017 Implemented a slightly more sophisticated matching algorithm: convert descriptions to lower case, if one description is contained in the other then they match. If they do not then split the descriptions into words and throw away duplicates if the resulting sets or words differ by less than 20% of the words then they match.
v1.0 04/03/2017