Pywps 4.2.1 implementation

[jorgejesus]

Overview

Implementation of pywps 4.2.1 Ticket #49 It implements docker images that were tested with new pywps 4.2.1

Related Issue / Discussion

The current dockerfiles point to the pywps_4.2 branch, this is a sort of chickend and egg problems since docker images point to pywps-flask and from there to the new pywps version

requirements have been change to point to pywps number version tags

Additional Information

If PR is approved it is necessary to path the dockerfiles on master to point to the proper locations. With PR approval it will be see the automatic build in dockerhub and

Contribution Agreement

(as per https://github.com/geopython/pywps/blob/master/CONTRIBUTING.rst#contributions-and-licensing)

• [ ] I'd like to contribute [feature X|bugfix Y|docs|something else] to PyWPS. I confirm that my contributions to PyWPS will be compatible with the PyWPS license guidelines at the time of contribution.
• [x ] I have already previously agreed to the PyWPS Contributions and Licensing Guidelines

[cehbrecht]

@jorgejesus I personally prefer to use conda environments instead of virtualenv. You can also install gdal using conda. If you like I can add the "conda way" as follow-up of this PR.

[cehbrecht]

... building gdal from source takes long when building the docker images. Using conda for docker builds could be an alternative ... maybe for later.