#338 Fix errors in CML loader with pseudo atoms

[SunFellow]

• Loading CML format: throw an exception on pseudo atom, if not query. This forces the caller to retry loading as QueryMolecule.
• Set Pseudo Atom property also for Carbon, which elementType was kept "C" at previous steps for pseudo atoms: AH, QH, XH, MH, X, M.
• Python test that repeats the essential logic of indigo-service /v2/convert.
• C++ test for debugging.

[mkviatkovskii]

Dear @SunFellow, Could you please tell me the current state of this pull request? Are there any blockers?

[MysterionRise]

@SunFellow is it still actual?