Added glfw3-es template for GLES contexts using GLFW3.

The only changes in comparison to original `glfw3` template are:

 * Removed core/compatibility profile distinction.
 * Replaced 'VERSION_1_0' etc. branch with GLES-specific values.
Merge branch 'testing' of https://github.com/ginkgo/flextGL into gles
Slightly changing syntax of profiles for es version declaration