striped stored series compiles code excessively

[kthielen]

The logic as currently implemented looks like this:

    void record(const K& k, const void* v, bool signal = true) {
      auto d = this->dmap.find(k);
      if (d != this->dmap.end()) {
        d->second->record(v, signal);
      } else {
        auto* s = new StoredSeries(this->c, this->db, 0, this->vty, this->bsize, this->sm);
        this->pmap.insert(k, s->rootRef());
        this->dmap[k] = s;
        s->record(v, signal);
      }
    }

This results in one compile phase per unique key, but nothing unique is compiled in each case and instead the compile step can be factored out and done once.