Release 0.1.0

[130s]

Changes in this PR

• For all packages,
  • Add CHANGELOG.
  • Bump versions in package.xml.
• Locally generated tag but haven't pushed it yet. Since I'm unsure if I'm expected to make releases yet (offered at https://github.com/ros-industrial-consortium/packml/issues/46#issuecomment-507386875), I haven't tried pushing it to the remote origin.
• Also, not really related to release, but updated CI config to:
  • Add ROS Melodic.
  • Add ROS pre-release testing (allow to fail. This won't pass unless the package is listed on rosdistro, which is not yet the case for packml. Only useful once it's released).