https://issues.liferay.com/browse/LRDOCS-926

LRDOCS-926 Added information to the Upgrading Social Office section on the necessity of applying any available fix packs before upgrading to SO 3.0. Pointed to User Guide's section on portal upgrades. Added note about JBoss issue and workaround. Added note that SO configurations is now available in both SO 3 CE and EE. Added note that the Welcome theme has been removed in SO 3