ansible-role-install-ros2-ubuntu

[IMPROVEMENT] Support for both Ubuntu 18.04 / ROS2 Dashing & Ubuntu 20.04 / ROS2 Foxy

[IMPROVEMENT] Add more time before expect times out to allow dead slow connections to be able to terminate the download

[UPDATE] Allow more "buffer" for expect during the unattended installation of RTI DDS

[IMPROVEMENT] Use fact to hold RTI package name for more well-behaved when clause

[BUG] Correct default ROS2 distro to dashing