Contributor and licence agreements

# Overview

As part of OSGeo incubation, our Graduation Checklist (https://github.com/geopython/pywps/wiki/ProjectGraduationChecklist) requires the project to firm up contribution agreements.

This applies to the PyWPS software code files.

This is outlined in https://github.com/geopython/pywps/blob/master/CONTRIBUTING.rst#contributions-and-licensing. Template for completing the agreement (per https://github.com/geopython/pywps/blob/master/CONTRIBUTING.rst#contributions-and-licensing-agreement-template).
# Template

Hi all, I'd like to contribute to PyWPS. I confirm that my contributions to PyWPS will be compatible with the PyWPS license guidelines at the time of contribution.

Committers and contributors can either agree either via the pywps-dev mailing list, or here in this ticket.

All committers and contributors are listed at https://github.com/geopython/pywps/graphs/contributors
# Checklist

(PyWPS "master", aka PyWPS-4 branch)
## Committers
- [x] @jachym Jachym Cepicky
- [x] @jorgejesus Jorge Samuel Mendes de Jesus
- [x] @ldesousa Luís de Sousa
- [x] @tomkralidis Tom Kralidis
## Contributors
- [x] @mgax Alex Morega
- [x] @Noctalin Calin Ciociu
- [x] @SiggyF Fedor Baart
- [ ] @jewie
- [x] @jonas-eberle Jonas Eberle

---
### Contributor to older versions of PyWPS (< 4.x)
- [x] @cehbrecht
- [x] @ricardogsilva Ricardo Garcia Silva
- [x] @gschwind Benoit Gschwind
- [x] @khosrow Khosrow Ebrahimpour
- [ ] @TobiasKipp Tobias Kipp
- [x] @kalxas Angelos Tzotsos
- [x] @Kruecke Florian Klemme
- [x] @slarosa Salvatore Larosa
- [x] @ominiverdi (Lorenzo Becchi)
- [x] @lucacasagrande (doktoreas - Luca Casagrande)
- [ ] @sigmapi (pana - Panagiotis Skintzos)
- [ ] @fpl Francesco P. Lovergine
- [x] @giohappy Giovanni Allegri
- [x] sebastianh Sebastian Holler
- [ ] Soeren Gebbert