Microsoft-published custom visuals as default

Include all Microsoft-published Custom Visuals as part of Power BI desktop and Power BI service. This change will allow users to more easily select different types of visualizations for their reports. This change would also remove some of the poor user experience of seeing the nagging warning "danger! There's a potentially malicious custom visual in this report". If the visual is built by Microsoft it should be able to pass a security muster and thus be safe to run in all circumstances.