Renaming Changes

[ryanlevy]

This PR will do 4 things:

• Rename some internal variables so that we never overload the function dimension
  • This includes an API change that functions like exp_itn(s; dimension=2) -> exp_itn(s; dim=2)
• Rename calculate_fxyz and calculate_fx to just evaluate and not differentiate between 1d and multi-d (Suggested by @emstoudenmire )
• Rename calculate_x and calculate_xyz to calculate_p
• Rename/merge delta_x and delta_xyz to delta_p