add xenial builds for RStudio; server-only til we figure out qt
add xenial builds for RStudio; server-only til we figure out qt

JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,JanMarvin/rstudio