Decrease dependencies in generated packages

[grantweiss-RaymondCorp]

It looks like bloom is using the run_depends key from the catkin_pkg Package class. The run_depends key is from package.xml version 1, version 2 removed this key to break it out into slimmer exec_depends and build_export_depends (REP 140). It looks like catkin_pkg will populate the newer keys when the input is a package.xml version 1.

In perception_pcl, I am able to remove over 2gb of dependency install (libpcl-dev) by making bloom-generate use exec_depends only.
ros-perception/perception_pcl#475

I am unsure of backwards compatibility testing and intended behavior so held off on a PR.

[cottsay]

The reason that run_depends is used here is that ROS packages are not split into runtime and development subpackages, so the single package serves both roles. This means that when installing a ROS package, we need not only the dependencies needed to run the binaries contained in that package, but we also need to install the dependencies necessary to build a downstream package, a role typically served by a -dev subpackage.

If/when we find a clean way to split ROS package generated by Bloom into runtime/dev subpackages, it would behave as you're expecting here.