Add BUILD.bazel files to drake_ros_* packages

[sloretz]

The drake_ros_* packages are CMake packages. This is convenient when working with tools in the ROS ecosystem. This is a ticket for adding BUILD.bazel files to those packages. That makes them convenient to include in a bazel workspace for those using Drake with bazel.

Attached is a bazel workspace example using #23 to display a capsule from a Drake multibodyplant in RViz using bazel.

capsule_example.tar.gz

[sloretz]

@gbiggs FYI The capsule_example.tar.gz link is the code for this: #23 (review)

[sloretz]

This is complete for drake_ros_core, drake_ros_tf2, and drake_ros_viz. Only drake_ros_examples needs to be bazelized now.