Merge remote-tracking branch 'upstream/develop' into develop
Merge remote-tracking branch 'upstream/develop' into develop
Move cropping and texture and font rendering into CanvasRenderer
Handle case where there are no GUI hud elements
Replace Sys calls with EngineTime getRawTimeInMs
HeadlessShader shouldn't be abstract
HeadlessMaterial doesn't correctly set material data field
Fixing incorrect method used.
Added the two most common interpolation functions
Merge pull request #901 from MarcinSc/develop

Fixing incorrect method used.
Added the UIDoubleSlider widget
Cleanup
Undoing unintended changes
Use DisplayDevice isHeadless for registering systems

Rename Display to DisplayDevice

Move opengl from StateInGame to DisplayDevice

Remove resizeViewport() and wasResized() and fold them into calling lwjgl classes

Verify DisplayDevice is registered
Merge pull request #903 from mkienenb/PR-no-GUI-HUD-bug

Handle case where there is no GUI hud
Merge pull request #904 from mkienenb/PR-remove-Sys-References

Replace Sys calls with EngineTime getRawTimeInMs
Merge pull request #905 from mkienenb/PR-headless-bug-fixes

Pr headless bug fixes
Isolate lwjgl timer specifics
Sleep 1000 microsecs if no delta change to prevent busy-waiting
Merge pull request #910 from mkienenb/PR-Time

Isolate lwjgl timer specifics