Skip writing out coordinates if the 'coords' section is provided in orcablocks

This is a simple change to the write_orca function for the Orca I/O to skip writing out the coordinates if the 'coords' string is found in the orcablocks parameters. This will be useful for users that want to make more specific inputs for the coordinates to e.g., place point charges or effective core potentials at specific positions for embedding. Could you please review this @AndrewRosen.