wildcardquery has logic to rewrite to termquery if there is no wildcard character, but
- it needs to pass along the boost if it does this
- if the user asked for a 'constant score' rewriteMethod, it should rewrite to a constant score query for consistency.
additionally, if the query is really a prefixquery, it would be nice to rewrite to prefix query.
both will enumerate the same number of terms, but prefixquery has a simpler comparison function.