modules: added FindOpenGLES3.cmake.

So we are able to build the examples on ES3 too.
viewer: make the example usable on OpenGL ES.

We do have `ports` branch for ES ports, but this is such small change
that it won't hurt if this is exposed to the users in the example
documentation.
Added Jenkins CI configuration.

Just to verify that we are able to built the examples, nothing more.
Merge branch 'master' into compatibility
package: compatibility version of Jenkins CI configuration.