Molsystem

* Handle uncertainties in CIF files expressed as '(x)' at end of value.

* Improved naming of molecule in QCSchema
* Added creation of configurations from QCSchema objects.

2022.11.20 -- Added a method to copy a configuration.
Added a new method to the `system` class, `copy_configuration`, that creates a copy of
the configuration using the same atomset and bonset, but new coordinates and cell so
that any changes to coordinates and cell are not shared between the configurations. By
default it copies the current configuration.

The total charge and multiplicity were not correctly set when creating an Open Babel
molecule.

Added methods for straining the unit cell, and also straining a configuration,
correctly handling the coordinates for an affine transformation. In the future will
add e.g. affine transformation of the centers of molecules, which is useful for
molecular fluids.

Added the system for properties, in addition to the configuration. This allows system
properties that are not associated with a particular configuration, which is often
appropriate for experimental results. It also makes it much easier to search for
systems where any configuration has a particular property.

2022.10.26 -- Improved database write performance.
Switched to write-ahead mode and tweaked memory settings. This gives a large
performance improvement (10x or more) for large database (~1 GB).