Updates:
* updated CML with more simulations in ebeam_dc_halfring_straight
* updated example ring resonator layout
* Waveguide: DevRec with 10X fewer points
* many PCell fixes
* fix for "Stream has unknown format" (hopefully)
New PCells in EBeam-dev (development library, no compact models):
* Contradirectional grating coupler PCell, both straight and spiral
* Apodized Bragg grating
* Spiral Bragg grating
* Photonic crystals
* sub-wavelength fibre grating coupler