(doc) Added general build status badge
(doc) Added general build status badge

Will need to figure out if it is possible to get individual badges for builds within the matrix
cake-build/cake,gep13/cake,devlead/cake,gep13/cake,mholo65/cake,cake-build/cake,mholo65/cake,patriksvensson/cake,patriksvensson/cake,devlead/cake