Incorrect loading of chain identifiers from PDB files

The issue must be fixed and tested until Nov. 18!!

In the current UGENE version names of chains, loaded from a PDB file, are numerical. This is incorrect. The names are available in the PDB format and must be used in the UGENE GUI - use chain identifier field from the "ATOM" records.

For details see the use cases below, the attached screenshots, and the format specification:
http://www.wwpdb.org/docs/documentation/file-format/PDB_format_1996.pdf (p.174 - the chapter about "ATOM")

Use case 1:

1. Open a PDB file with several "MOLECULE" records (e.g. 1FDL).
   Expected state: The correct chain names are shown in the Project View and in each single-sequence view of the Sequence View.
2. Open an annotation node in the Annotations Editor to see its qualifiers.
   Expected state: There is "molecule_name" filed. It has a correct molecule name, read from the PDB file header, NOT the chain name.
3. Select "Structural Alignment > Align With" item in the context menu.
   Expected state:
   • The correct chain names are available in the "Chain" menu.

Use case 2:
The same as UC1, but use a PDB file with molecules that have several chains, i.e. the comma-separated list of chain identifiers (e.g. 3INS).