Implement ict::find_n

[intrig]

Currently, ict::find() returns the first item it finds. Implement:

template <typename Cursor>
std::vector<Cursor> find_n(Cursor parent, const path & path, 
     size_t max = std::numeric_limits<size_t>::max())

This wil return all matching items, up to max.

[wythe]

This should be for_each() with a lambda for matching. It is similar to recurse(). Need to revisit this later.