[FEATURE] Option to use global formation summary thickness file

[markjessell]

Is your feature request related to a problem? Please describe.
For the Hamersley stitch it would be great to use a single formation thickness file compiled from all the tiles

Describe the solution you'd like
A flag and file path that allows a single formation thickness file to be accessed. Same format as individual ones.

Describe alternatives you've considered
Having the notebook switch the file in each time = [clunky]

Additional context
Add any other context or screenshots about the feature request here.

[markjessell]

Having said that having local variations in thickness is also helpful. So maybe we need a combination of global when we have no choice (and if available) and local when available?