Add new interface to getShapeActorMap
Add cmake option to choose HTML file suffix for Sphinx
Update Sphinx layout.html file
Add Sphinx CSS stylesheets
PCLVisualizer: save and restore camera information

Press ctrl + s to save camera parameters and ctrl + r to restore the
saved camera parameters.

If a camera file is specified with "-cam" option or pcd file(s) is(are)
available in the command line, the camera parameters will be written to
the corresponding file and can be restored later from that file.
In this case, PCLVisualizer will restore camera parameters automatically
from the corresponding file when the pragram restarts with the same
command line input.
Replace gtest with sytem version

- Add new FindGtest.cmake to find installed versions.
- Add libgtest-dev for Travis
Fix small formatting errors