Add generalised name generator and use in atom/instrument editor and output names

[oerc0122]

Description of work
Add a new function to generate names based on a template.

Fixes #1097

Fixes

• New get_next_name function
• Minor typing/name fixes in atom editor

To test

• Run doctests
• Copy atoms in editor
• Try duplicate filenames
• Try duplicate instruments

[MBartkowiakSTFC]

The analysis runs now use names that all start with "output", e.g. "outputTemperature_result1.mda". We probably don't need both "output" and "result" in the output file name.

More importantly, at the moment trying to copy the same atom twice in the element property editor blocks the GUI permanently.