Fbpic

This is a minor release, that makes improvements to the PML and to the documentation.

- The PML should now be slightly faster on GPU (due to the suppression of
unnecessary host-device communications: see [423](https://github.com/fbpic/fbpic/pull/423))
- The particles do not gather the fields in the PML anymore: see [424](https://github.com/fbpic/fbpic/pull/424).
- The documentation has a new section on 3D rendering: see [426](https://github.com/fbpic/fbpic/pull/426).
- The documentation and code of FBPIC is now compatible with `openPMD-viewer 1.0.0`: see [428](https://github.com/fbpic/fbpic/pull/428)
and [427](https://github.com/fbpic/fbpic/pull/427).

This release adds the possibility to add Perfectly-Matched Layers in the
radial dimension (see [417](https://github.com/fbpic/fbpic/pull/417)).
As part of this change, the user is now expected to pass a dictionary
for the argument `boundaries` of the `Simulation` object (instead of a
single string) ; for instance: `boundaries={'z':'open', 'r':'reflective'}`.
The PML in the radial direction are activated by passing `'r':'open'`.

In addition, several others changes have been included in this release:

- It is now possible to use FBPIC with numba 0.46 and cupy 7
(see [414](https://github.com/fbpic/fbpic/pull/414)).
- The default phase of the `FlattenedGaussianLaser` has been updated.
(see [411](https://github.com/fbpic/fbpic/pull/411))
- A new laser profile has been added: `FewCycleLaser` which is well-adapted
for tightly-focused, short laser pulses (see [403](https://github.com/fbpic/fbpic/pull/403)).

This release fixes two important issues in FBPIC:

- There was a bug on GPU, related to particle sorting (see
[402](https://github.com/fbpic/fbpic/pull/402) for more details). This bug
mostly affected simulations with ionization, and typically results in additional
ionization occurring in arbitrary locations in the simulation box
(See [396](https://github.com/fbpic/fbpic/issues/396)). In addition, this
bug could have also affected simulations without ionization, and would result
in an incorrect particle push, for a fraction of the particles. It is now fixed.

- Particles that exit the simulation box radially used to still feel the
fields from the last cell of the box. This could cause these particles to
be pushed back into the box (see [369](https://github.com/fbpic/fbpic/issues/369)).
This is now fixed: with the new version of the code, particles that exit the box
radially do not feel any force from the grid anymore, and move in a straight line
(see [398](https://github.com/fbpic/fbpic/pull/398)).

This is a bug-fix release ; it prevents an incompatibility between cupy and the latest version of numba (numba 0.46).
In addition, a new diagnostic was added, in order to save the input script.

This is a bug-fix release ; it fixes a minor bug with Python 2, for the
back-transformed particle diagnostic (see [389](https://github.com/fbpic/fbpic/pull/389)).

This is a minor release. It introduces:

- A minor API change: When creating a `Simulation` object with no particles,
the user does not need to do `sim.ptcl = []` anymore: [376](https://github.com/fbpic/fbpic/pull/376)
- FBPIC is now compatible with the upcoming version 1.0 of `openPMD-viewer`: [387](https://github.com/fbpic/fbpic/pull/387)
- A bug-fix for the ballistic injection in the lab-frame: [384](https://github.com/fbpic/fbpic/pull/384)
- Limited, rudimentary support for PICMI: [350](https://github.com/fbpic/fbpic/pull/350) [#383](https://github.com/fbpic/fbpic/pull/383) [#384](https://github.com/fbpic/fbpic/pull/384) [#384](https://github.com/fbpic/fbpic/pull/384)