Read-structure-step

* Switched to new handling of system and configuration names as properties in SDF
files, rather than encoded in the title. This avoids problems with special
characters in name, for example when using SMILES as the name.

2025.1.15 -- Added ability to write using an arbitrary list of structures.

* If the XYZ file had the charge and spin multiplicity encoded in the comment line,
and the spin multiplicity came before the charge, the spin multiplicity was not
correctly set. This fixes that issue.

* Added more keywords to the header of XYZ files to allow for more flexibility in
reading them. Specifically 'title', 'model', and 'name', which can be used to name
the system and/or configuration.
* When reading SDF files, 'keep current name' will use the encoded system name in SDF
files written by SEAMM, if it exists.
* Fixed minor issue writing SDF files where the 'configurations' widget was displayed
when writing the current configuration. The widget is now correctly hidden.

2024.12.29 -- Bugfix: Issue with reusing systems matching SDF files.
* The logic was faulty, so if the first structure in an SDF file was a configuration
of an existing system, it was not added to the system correctly.

* The molsystem was updated to improve the handling of properties. This required
changes in this module to match the new molsystem.

* Fixed syntax of the properties pulled out from MOPAC encoded parameterization
inputs.