Made it possible to reverse group, doc and docgroup properties.

Hit properties could already be reversed. Just call .setReverse on the
property to reverse it. When serializing/deserializing, reversed
properties will be prefixed with a dash, e.g. "wordleft,-wordright".
Renamed getContentPosition to ..Character.., added getWordPosition.

These names more clearly state what each method returns, avoiding
confusion.
Always copied settings when constructing one Hits obj from another.