Update Process documentation

[fklemme]

As the catalog of services has changed recently, the documentation could use some update/rework. See: http://birdhouse-hummingbird.readthedocs.org/en/latest/processes.html

[cehbrecht]

This is an ongoing task ... but we have now the nicely rendered process descriptions using the pywps Sphinx extension:

https://birdhouse-hummingbird.readthedocs.io/en/latest/processes.html

Detailed information for the processes is referenced by metadata links.