Revive wide-angle camera tutorial

[scpeters]

The wide-angle camera tutorial was previously available at the following URL corresponding to a pull request branch that was never merged.

• http://gazebosim.org/tutorials?tut=wide_angle_camera&branch=wideanglecamera#PluginExample

It references an unmerged gazebo branch: https://github.com/osrf/gazebo/compare/gazebo7_7.0.0...wideangle_example_7.0.0?expand=1

Prior pull requests:

• https://osrf-migration.github.io/gazebo_tutorials-gh-pages/#!/osrf/gazebo_tutorials/pull-requests/265/page/1?slug=wideanglecamera
• https://osrf-migration.github.io/gazebo_tutorials-gh-pages/#!/osrf/gazebo_tutorials/pull-requests/277/page/1
• https://osrf-migration.github.io/gazebo-gh-pages/#!/osrf/gazebo/pull-requests/1941/page/1

It includes an old example GUI plugin using gazebo7 and qt4 that would need to be updated for use with currently supported versions of gazebo.