Seamm

* Removed debug printing that was accidentally left in the flowchart code.

* Added a subflowchart step to allow calling another flowchart from within a
flowchart.
* Added copy/cut/paste for flowcharts in the menus and shortcuts
* Enhanced the menus and bindings for operations on flowcharts so that they act on
the currently active flowchart or subflowchart.

* Removed directories and files not ending in ".flow" from the list of flowcharts
that can be opened.
* When getting a flowchart from a previous job, the list of jobs is reversed so
the most recent is at the top.
* Enhanced the handling of parameters to support e.g. lists of values with the
normal units attached. Used in e.g. thermochemistry to allow lists of temperatures
and pressures with associated units.

* Fixed a problem converting e.g. E_h to kJ/mol in the GUI widgets. The problem
occurred whenever the conversion was not direct but involved different
quantities.
* Internal enhancement: exposed the metadata to graphical nodes as a property.

* The standard structure handling widgets and methods had an error is the approach
was a variable rather than one of the choices.

* Added multiple axes to line graphs.
* Updated to correct version of plotly. 'latest' is actually not.