feat: Add theme/config-point capability and docs. (#2641)

This is the initial addition of the config point settings to allow run time loading of GUI settings via "theme" files/parameters.
The intent is to add an example PR that shows when to use config point, how to configure it, write documentation for it etc.

extensions/cornerstone/src/commandsModule.js

@@ -186,7 +186,7 @@ const commandsModule = ({ servicesManager, commandsManager }) => {
         }
 
         const viewportInfo = getEnabledElement(i);
-        const hasCornerstoneContext =
+        const hasCornerstoneContext = viewportInfo.context &&
           viewportInfo.context === 'ACTIVE_VIEWPORT::CORNERSTONE';
 
         if (hasCornerstoneContext) {