message: Add generic implantation of factory for time stopping criterion. See
diff: @@ -44,10 +44,26 @@ namespace stop {
  class Time : public Criterion {
  public:
  using clock = std::chrono::system_clock;
  - class Factory : public Criterion::Factory {
  - /* generic factory implementation */
  +
  + struct Factory : public Criterion::Factory {
  + using t = std::chrono::seconds &;
  +
  + Factory(t v) : v_{v} {}
  +
  + static std::unique_ptr<Factory> create(t v)
  + {
  + return std::make_unique<Factory>(v);
  + }
  + std::unique_ptr<Criterion> create_criterion(
  + std::shared_ptr<const LinOp> system_matrix,
  + std::shared_ptr<const LinOp> b, const LinOp *x) const
  + {
  + return std::make_unique<Time>(v_);
  + }
  + t v_;
  };
  +
  Time(std::chrono::seconds limit)
  : limit_{std::chrono::duration_cast<clock::duration>(limit)},
  start_{clock::now()}
  