Database update script should run as web user

Some parts of mediawiki, such as the UIDGenerator, create temporary files
owned by the executing user.  Scripts such as the database update
script must run as the same user as the webserver so that permission
conflicts do not occur due to varying uid.

Change-Id: Ic674d7b7f17e3878632e200b5ac91fdb448789d8
Create flow role

Both Flow and VisualEditor can require parsoid, as such parsoid
was made into an independant role so flow and ve can independantly
declare the dependancy.

Change-Id: Ic8d07787a24b10bfc46ed93a43d32767818c96b9