Abstract DictionaryAnchor into a KeywordAnchorBase

[WarmCyan]

KeywordAnchorBase has a list of keywords and the string textfield widget to interact with it

DictionaryAnchor is then a normal positive BoW, but this allows easily creating other subclasses for negative keyword anchors #5 and so on so forth. This would also entail the +new buttons being able to have a default anchor type.