#230 add cell tracking Issue created by d-m-bailey When using multiple search paths and combining cells from different locations, it is unclear where the final data is loaded from. It would be helpful to have at least one of the following capabilities. 1. when a cell is loaded, display the absolute path (and possibly relative path). eg. cellA at relativePath loaded from /absolutePath 2. when gds is written, print the absolute path of the mag data for each cell 3. add a command option that prints the relativePath/absolutePath of each cell loaded RTimothyEdwards/magic