Thank's for posting 
Have you tried using the FULLSCREEN
mode yet?
You can set this either in the config.properties
-> gfx_fullscreen=true
or via configuration from code directly: Game.config().graphics().setFullscreen(true)
.
Inspired by this post
I'm currently investigating this and I'm working on extending the engine, so you can chose between the following display modes:
WINDOWED = Resizable Window with decoration (otherwise it would not be resizable)
BORDERLESS = Basically windowed but without decoration and scaled to the entire screen
FULLSCREEN = Native Fullscreen; locked to the framerate of the Monitor
I think a "borderless windowed" mode is not really something that occurs in practice.
These new options will replace the mentioned "fullscreen" boolean option with the new configuration gfx_displayMode
that you will be able to set from code via Game.config().graphics().setDisplayMode(...)
You can expect these changes with the next engine release v0.4.18-alpha
by the end of this year.