Tasks for glvis-4.0 release

[tzanio]

Must Have

• Merge OpenGL modernization #66 (@tzanio, @v-dobrev, @kanye-quest)
• Switch to a BSD license BSD Relicense #115 (@tzanio, @acfisher)
• Consider other API-breaking changes, e.g. keystroke re-assignment?
• Merge Final changes for glvis-4.0 #123
• Update website, Website updates for glvis-4.0 release web#1

Important

• Make sure EMSCRIPTEN code works (@tomstitt)
• Address Building issue with MFEM built with MPI support on Linux #120 (see Another fix for MPI+X11 error #121)
• Merge Fix a build issue on Ubuntu #125
• Merge move mesh division in 2d to key 'o' for consistency with 3d #126

Nice to Have

• Resolve Black screen with VNC on remote CentOS7, "Window type not found" through X11 #112 (@kanye-quest )
• Resolve How to plot each element of mesh with colormap #116 (@v-dobrev )
• Address Are the "cutting plane" and "clipping plane" the same thing? #107, Displays element and vertex numberings, but not dof numberings #106 , Inconsistency between key commands in 2D and 3D #99 (@rw-anderson)
• Resolve VTK xml file support with high order lagrange elements #64 (@pazner)

After the release

• Update Spack package
• Update MFEM examples + miniapps for new keys
• Update GLVis website examples for new keys, Updating the keys in the web docs after glvis-4.0 web#2
• Fix GLVis scripts and simplify glvis.cpp, Refactor glvis main file; fix for segfault on glvis script #130
• Update pyglvis, Modularize glvis-js and add npm package config glvis-js#1, use glvis module from glvis-js pyglvis#2
• Add CI testing, Add CI testing with GitHub Actions #124