Correct variable name overlap in int2cart

[joaomcteixeira]

Corrects a variable name overlap in int2cart in build. There was no bug, but the var names were prone to bugs in the future. Better correct them now.

[JerryJohnsonLee]

I am not sure this is exactly the best thing to do.. The reason I make it the same name as the original bond length list is that they serve the same purpose: a list of bond lengths for the current residue in order of [N-CA, CA-C, C-N]. If we change this name then in the future if we need to use this list we need to do additional if-statements to decide which list to use depending on the bgeo strategy, right?

[menoliu]

I cannot foresee any bugs that may arise from this but I think having a different variable name to store different angles/lengths from different strategies is just better programming form? Also if we're to change bond_lens we should also change bend_angles to follow the same format (though I can see why you didn't change it because _bend_angle and not _bend_angles is used for the rest