Move to placing Ubuntu repos into sources.list.d

add-apt-repository writes to /etc/apt/sources.list only unless the repo is a PPA. This can cause problems when using something like cloud-init, that by default clobbers the file with it's own template.

It is also better practice to use the sources.list.d approach to add in more repos instead of appending to sources.list

Add TDL documentation and update RNG