Enable mouse rotate, pan, and zoom with TrackballControls

src/dyna3.litcoffee

@@ -3,7 +3,9 @@
 When you load dyna3, you should initially see a three-dimensional coordinate system with labeled axes.
 ```javascript
 
-    import {threeLoaded, three as J3} from './externals.js'
+    import {threeLoaded,
+        three as J3,
+        TrackballControls as J3x} from './externals.js'
 
     LTx = { dashed: true, plain: false }
 
@@ -48,7 +50,11 @@ When you load dyna3, you should initially see a three-dimensional coordinate sys
         camera = new J3.PerspectiveCamera 75, rwd/rht, 0.1, 1000
         camera.position.z = 5
 
-        renderer.render scene, camera
+        controls = new J3x.TrackballControls camera, renderer.domElement
+
+        renderer.setAnimationLoop ->
+           controls.update()
+           renderer.render scene,camera
 
     threeLoaded.then main
 ```

src/helpers/pkglock_to_externals.litcoffee

@@ -4,7 +4,7 @@
 
 The dyna3 program depends on some externally-maintained JavaScript libraries/modules. The package uses npm to track these external dependencies. A module externals.js is automatically generated from the package.json and package_lock.json files created by npm to load the necessary modules at runtime.
 
-The generation is performed by pkglock_to_externals.litcoffee, which also records the main importable file within the library, as there does not seem to be a systematic way to generate that filename from the module name.
+The generation is performed by pkglock_to_externals.litcoffee, which also records all of the needed importable files within the library, as there's no way to generate that from the module name or the information in package-lock.json.
 
 Specific packages/implementation approaches for components of dyna3 include the following items. All packages are obtained from npm unless otherwise noted.
 
@@ -15,7 +15,10 @@ Specific packages/implementation approaches for components of dyna3 include the
 
 ```javascript
 
-    importable = { three: 'build/three.module.js' }
+    importable =
+        three:
+            three: 'build/three.module.js',
+            TrackballControls: 'examples/jsm/controls/TrackballControls.js'
 
 ```
 And here is the current complete list of external libraries on which operation of dyna3 depends:
@@ -38,19 +41,31 @@ And here is the current complete list of external libraries on which operation o
         if process.argv.length > 2
             process.stdout.write "- #{dep}\n"
         else
+            exports = (
+                "export var #{mod};" for mod in Object.keys importable[dep]
+            ).join "\n"
+
+            mainload = (
+                "#{mod} = await import('https://cdn.jsdelivr.net/npm/#{dep}@#{pldata.dependencies[dep].version}/#{importable[dep][mod]}');" for mod in Object.keys importable[dep]
+            ).join "\n        "
+
+            fallbackload = (
+                "#{mod} = await import('./node_modules/#{dep}/#{importable[dep][mod]}');" for mod in Object.keys importable[dep]
+            ).join "\n            "
+
             block =
             """
-            export var #{dep};
+            #{exports}
             export var #{dep}Loaded = new Promise(async function(resolve, reject) {
                 var success = false;
                 try {
-                    #{dep} = await import('https://cdn.jsdelivr.net/npm/#{dep}@#{pldata.dependencies[dep].version}/#{importable[dep]}');
+                    #{mainload}
                     console.log('CDN import of #{dep} module OK');
                     success = true;
                 } catch(err) {
                     console.log('CDN import of #{dep} failed: ' + JSON.stringify(err));
                     try {
-                        #{dep} = await import('./node_modules/#{dep}/#{importable[dep]}');
+                        #{fallbackload}
                         success = true;
                     } catch(err) {
                     }