Addition of PaaS

Add the following commands to the OSM Client:
 - osm paas-add
 - osm paas-delete
 - osm paas-update
 - osm paas-list
 - osm paas-show

Change-Id: I5a0ba86c2b3a6a9239c2f336c33a0777cc72654b
Signed-off-by: Patricia Reinoso <patricia.reinoso@canonical.com>