WPS services implementation

[imincik]

Implementation:

• All GRASS modules will be exported by "--wps-process-description" option. There is also toolboxex.xml file with description organization structure of GRASS modules
• Process builder plugin for QGIS will be created with capability to load the list of exported GRASS modules and create the final process
• Processes will be served by PyWPS4
• We will add possibility to attach WPS processes to GIS.lab Web QGIS plugin
• WPS client for GIS.lab Web will be created once the application will be moved to OL 3
• WPS services will run under GIS.lab's OWS load balancer

Note by @wenzeslaus:

• it would be fine if all grass modules would be exported as raw processes beside user created processes

QGIS Processing:

• http://www.3liz.com/blog/rldhont/index.php?post/2015/09/07/wps4server%3A-QGIS-Processing-to-Web-Processing-Service

[landam]

See #513