MolfileSaver add Data S-Groups to molecule at saveMolecule()

[AliaksandrDziarkach]

Create next UT in indigo-core-unit-tests:

TEST_F(IndigoCoreFormatsTest,mol_saver_issue)
{
    Molecule t_mol;

    loadMolecule(R"(
  -INDIGO-07262316452D

  6  6  0  0  0  0  0  0  0  0999 V2000
   -1.4617   -0.6508    0.0000 N   0  0  0  0  0  0  0  0  0  0  0  0
    0.0000    0.0000    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.3856   -0.8000    0.0000 N   0  0  0  0  0  0  0  0  0  0  0  0
    2.5747    0.2706    0.0000 N   0  0  0  0  0  0  0  0  0  0  0  0
    1.9239    1.7323    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.3327    1.5650    0.0000 N   0  0  0  0  0  0  0  0  0  0  0  0
  1  2  2  0  0  0  0
  2  3  4  0  0  0  0
  3  4  4  0  0  0  0
  4  5  4  0  0  0  0
  5  6  4  0  0  0  0
  6  2  4  0  0  0  0
M  STY  4   1 DAT   2 DAT   3 DAT   4 DAT
M  SLB  4   1   1   2   2   3   3   4   4
M  SAL   1  1   3
M  SDT   1 MRV_IMPLICIT_H                                                       
M  SDD   1     0.0000    0.0000    DA    ALL  1       1  
M  SED   1 IMPL_H1
M  SAL   2  1   4
M  SDT   2 MRV_IMPLICIT_H                                                       
M  SDD   2     0.0000    0.0000    DA    ALL  1       1  
M  SED   2 IMPL_H1
M  SAL   3  1   3
M  SDT   3 MRV_IMPLICIT_H                                                       
M  SDD   3     0.0000    0.0000    DA    ALL  1       1  
M  SED   3 IMPL_H1
M  SAL   4  1   4
M  SDT   4 MRV_IMPLICIT_H                                                       
M  SDD   4     0.0000    0.0000    DA    ALL  1       1  
M  SED   4 IMPL_H1
M  END
)", t_mol);
    ASSERT_EQ(t_mol.sgroups.getSGroupCount(), 0);
    Array<char> out;
    ArrayOutput std_out(out);
    MolfileSaver saver(std_out);
    ASSERT_EQ(t_mol.sgroups.getSGroupCount(), 0);
    saver.saveMolecule(t_mol);
    ASSERT_EQ(t_mol.sgroups.getSGroupCount(), 2);
    saver.saveMolecule(t_mol);
    ASSERT_EQ(t_mol.sgroups.getSGroupCount(), 4);
    saver.saveMolecule(t_mol);
    ASSERT_EQ(t_mol.sgroups.getSGroupCount(), 6);
}

This test passed which is wrong - Sgroup count should not increase after saveMolecule() and should keep value 0.
This is result of MolfileSaver option add_implicit_h incorect processing in saveMolecule().

        bool add_implicit_h;  // If true then MRV_IMPLICIT_H Data S-groups will be added for saving
                              // the number of implicit H for aromatic atoms
                              // (if it is required for correct de-aromatization) (default value is true)

Instead of adding Sgroups to molecule temporary MoleculeSGroups variable should be used.