Phidl

New features
- `D.remove()` can now remove Ports as well as references/polygons

Bugfixes
- Can't have a major release without at least one bug! Fixed errors introduced by optimized-rotation algorithm.

New features
- Significant upgrades to `quickplot2`: now shows coordinates, a help message box (press ?), and a scale notation (along with several under-the-hood optimizations)
- Added `D.hash_geometry()` -- use to generate a SHA1-based hash of the polygons in a Device
- Added `phidl.utilities.load_lyp()`, which loads a KLayout layer properties (.lyp) file and converts it into a LayerSet (contribution thanks to Alex Tait atait)

Changes
- Optimized rotation so 90-degree rotations (contribution thanks to Alex Tait atait)
- Function documentation for geometry module (contribution thanks to Jimmy Gammell jgammell and Dylan Oh dmwo)
- `pytest` implementation for internal consistency checking

New features
- Added `pg.union()` - a handy convenience function to join (union) polygons together, either by-layer or all together (see [tutorial](https://github.com/amccaugh/phidl/blob/master/phidl/phidl_tutorial_example.py) for full details)
- Added `phidl.utilities.write_svg()` - allows you to write your geometry directly to SVG for the sake of publishing figures easily (see [tutorial](https://github.com/amccaugh/phidl/blob/master/phidl/phidl_tutorial_example.py) for full details)
- Added pg.xor_diff(A,B) - Produces an XOR operation between Devices A and B, which can by used to compare differences between A and B (see [tutorial](https://github.com/amccaugh/phidl/blob/master/phidl/phidl_tutorial_example.py) for full details)
- Allow usage of a Python `set` (e.g. {3,5,6}) as an input to the `layer` argument of add_polygon (and thus all geometry-creation functions in phidl.geometry) to create the polygons on multiple layers. (see [tutorial](https://github.com/amccaugh/phidl/blob/master/phidl/phidl_tutorial_example.py) for full details)

Bugfixes
- None

Bugfixes
- Minor upkeep bugfixes

New features
- The addition of the argument `max_cellname_length` added to `D.write_gds()`. It is `28` by default, to guarantee maximum compatibility with GDS specifications (32 is generally the lower limit, and `write_gds()` applies a afterwards to prevent duplicate cellnames).
- New documentation backend (contribution thanks to Alex Tait atait)
- Added `D.remap_layers()` which allows you to to move all polygons contained on a layer within your Device to another layer. See [tutorial](https://github.com/amccaugh/phidl/blob/master/phidl/phidl_tutorial_example.py) for details
- Added `D.remove_layers()` which lets you remove all polygon geometry (optionally including labels) from a Device on the specified layers. See [tutorial](https://github.com/amccaugh/phidl/blob/master/phidl/phidl_tutorial_example.py) for details

Bugfixes
- Further fixes to `D.write_gds()` for rare edge cases