Siepic-ebeam-pdk

- improvements to scripted example layouts
- fixes to the Waveguide_SBend PCell
- fixes (DRC errors) to the ebeam_Bragg_te_1550 PCell
- layer table update

- improvement to loading WAVEGUIDES.XML files. Described at https://github.com/SiEPIC/SiEPIC-Tools/wiki/PDK-Maintenance

Fix:
- library registration problem
- cell: Waveguide SWG to strip
- shrink 50 MB down to 1 MB (suspected it caused trouble with Package Manager)

New:
- cell: thermal phase shifters, O and CL band, and for low-loss multimode waveguides
- cell: taper
- layer: deep trench
- DRC: recognition for mismatched pins

- fix issue with Path function; previously there was a "from pathlib import Path" which conflicted with "from pya import Path"
- SWG PCell: increase DevRec
- opt_in test label for ring resonator circuit examples

- loading library fix (import sys)
- Lumerical CML fix for ebeam_dc_halfring_straight component

- fix for CentOS7: removing ( and ) characters in filenames