Improved GLFW logical device driver

- transparency support
- allow resize of GLFW window
- corrected calculation of text height
- return correct screen size and metric information

Change-Id: I1673baf5b86078b20306798c202eaf19f363a2e6
Reviewed-on: https://iffwww.iff.kfa-juelich.de/review/103
Reviewed-by: Florian Rhiem <f.rhiem@fz-juelich.de>
Reviewed-by: Josef Heinen <j.heinen@fz-juelich.de>