Gdsfactory

- write_cells in gf.write_cells uses gdspy interface directly
- gf.import_gds has an optional gdsdir argument
- remove unused max_name_length parameter in gf.import_gds
- bring back matplotlib as the default plotter backend. Holoviews does not work well with some `sphinx.autodoc` docs
- add_fiber_array prints warning if grating coupler port is not facing west

- You can set up the default plotter from the gdsfactory config `gf.CONF.plotter = 'matplotlib'`
- [PR 142](https://github.com/gdsfactory/gdsfactory/pull/142)
- dispersive flag to meep simulations
- fixed bug where adding a layer would throw an error if "visible" or "transparent" were undefined in the .lyp file
- remove p_start (starting period) from grating_coupler_elliptical

- add Component.ploth() to plot with holoviews (inspired by dphox)
- Component.plot(plotter='holoviews') accepts plotter argument for plotting backend (matplotlib, qt or holoviews)
- use holoviews as the default plotting backend
- remove clear_cache from Component.plot() and Component.show(), it's easier to just do `gf.clear_cache()`
- remove `Component.plotqt` as the qt plotter is now available with `Component.plot(plotter='qt')`
- gf.geometry.boolean works with tuples of components or references as well as single component or Reference. Overcome phidl bug, where tuples are not trated as lists.
- Before plotting make sure we recompute the bounding box
- YAML mask definition allows using `settings` for global variables
- grating_coupler_rectangular first teeth starts next to the taper

- seal_ring accepts bbox instead of component
- die_bbox_frame accepts bbox
- die_bbox: rename text_position to text_anchor
- die_bbox: text_anchor accepts Literal instead of string

- Add [sidewall angles in MPB](https://github.com/gdsfactory/gdsfactory/pull/136)

- add some extra kwargs (with_taper1, with_taper2) to straight_heater_doped_rib
- add slab offset kwargs to cross_section.rib_heater_doped_contact