[types] add LineStrip3 impl (incomplete, similar to LS2), refactor template use in other line types, add :offset support for LS2/extrude, switch to BasicMesh as extrude default
add zero PArea template to LOB
[types] bugfix basic-mesh ctor calls in line ns
[webgl] add LineStrip3 conversion support
[webgl] add diffuse color support for Lambert shader, normalize transformed normal
[webgl] minor shader updates