Add ORCA bond stretch data

[adambaskerville]

One of the simple tests we are looking to run is to analyse the bond deviation from original length for a set of molecules. This will be done in batch MD simulations of ~ 100 frames; but we also want to analyse some simple heavy-light, heavy-heavy bond stretch PE surfaces and compare them against ground truth ORCA data. This will be run before the MD simulations as if the trained NNP cannot model a simple C-H or N-N bond stretch correctly then it will most certainly fail dowen the line so can be excluded immediately.

I have created a branch called add_orca_bond_stretch_data where I will add this.