Add support for alignment with offset/rotation

[pvnbhargava]

Currently PhotonicTemplateBase.add_instances_port_to_port() always co-locates the two ports provided as arguments, and assumes that they must abut each other to match orientation. However, ports can also be used as points of reference for placement without abutment.

One example of this is a double ring filter. The second ring should be placed relative to the first ring, but with a specified gap.