Siepic-ebeam-pdk

Additions:
- Verification output using KLayout's rdb & Marker Database Browser; easy to view errors in the KLayout tool

Improvements:
- multi-detector support for INTERCONNECT

Fixes:
- bug with verification; lists being over-written.

- Laser and detector PCells; user configures parameters
- netlist extraction
- Spice file generation
- call to Lumerical INTERCONNECT to simulate the Spice file; plot the results in a visualizer.

Updates:
- Python 3 / Windows compatibility: removed print ""; removed numpy
- menu item: delete extra top cells
- Correctly dealing with GUIDING_LAYER in ROUND_PATH waveguides, when user selects it
- waveguide length calculation added, including πr/4
- Spice netlist fixes -- tested that it works with Lumerical INTERCONNECT
- Added Lumerical INTERCONNECT launch to the menu
- waveguide - dialog for the radius
- floating point / rounding bug fixes
- Verification test GDS layout, to test/showcase capabilities.

Added Undo & radius dialog; bug fixes

New features:
- Menu item "W": selected paths are first snapped to the nearest pins, then converted to ROUND_PATH waveguides
- Menu item "Shift-W": selected ROUND_PATH waveguides on the silicon layer are converted to paths

PinRec text required on pins