jMonkeyEngine 3.8.0-alpha4

What's Changed

Fix Rendering Issue in PBRTerrain by @yaRnMcDonuts in #2365
LwjglWindow: solve window centering incorrect in JME 3.8.0-alpha3 by @stephengold in #2362
Fix: Incorrect mouse position on canvas LWJGL3 (Canvas) by @JNightRider in #2332
[Android] Fix Android JmeSurfaceView Memory Leak by @pavly-gerges in #2359
Fix missing wViewDir variable and undeclared/wrongly declared vars by @yaRnMcDonuts in #2367
Fix Fog in Lighting.frag by @yaRnMcDonuts in #2364
com.jme3.anim.tween.action.BlendSpace: basic javadoc by @pavly-gerges in #2022
Add RawInputListenerAdapter for easier listener creation by @capdevon in #2339
Revert "AnimComposer: return AnimLayer on the makeLayer and removeLayer methods." by @yaRnMcDonuts in #2378
SingleLayerInfluenceMask: fix serialization issues by @capdevon in #2372
update LWJGL from v3.3.4 to v3.3.6 by @stephengold in #2371
solve issue #2366 (bugs related to saving/loading a Spline) by @stephengold in #2368
#2379 Remove OSVR from JME VR by @richardTingle in #2380
update LWJGLX (AWT) from 0.1.8 to 0.2.3 by @JNightRider in #2373
update the groovy-test library to v3.0.24 by @stephengold in #2382
Finish Modularizing PBRTerrainUtils.glsllb by @yaRnMcDonuts in #2377

Full Changelog: v3.8.0-alpha3...v3.8.0-alpha4