#4228 [Stendhal trading] filtering for price range

[Kimmo Rundelin]

we can expect the trading list get very long on the main server, thus we need to:
1. ensure that the message sent to the player never gets too long
2. provide a way for the player to filter the the items on various criteria, like a word on the item name "show black", possibly filtering for price range too (suggested by kymara)

[Kimmo Rundelin]

Changed the description. Item name/type filtering is implemented now, and the player is given max 20 item list.