Revert "Trimmed the branch to only the gazebo_plugins sub directory"

This reverts commit 3716479c59c3b3369bb2869311768df7b360dd8c.
Rebase from 'upstream' (no changes)
Trimmed the branch to only the gazebo_plugins sub directory
Revert "Trimmed the branch to only the gazebo_plugins sub directory"

This reverts commit 0a013d42be6d9cafc97fa143ac9155ad771c82d9.
Rebase from 'upstream'
Trimmed the branch to only the gazebo_plugins sub directory