Java runtimes should be configured before projects are imported

[fbricon]

When you import projects, a didChangeConfiguration request triggers Java Runtime changes, that in turn triggers a full rebuild of the workspace.

I think we could improve the situation in BaseInitHandler.initialize, where we could do something like:

if (initializationOptions.get(SETTINGS_KEY) instanceof Map) {
  Object settings = initializationOptions.get(SETTINGS_KEY);
  @SuppressWarnings("unchecked")
  Preferences prefs = Preferences.createFrom((Map<String, Object>) settings);
  prefs.setRootPaths(rootPaths);
  preferenceManager.update(prefs);
  if (firstTimeWorkspaceIsOpened) {
    // We don't care about triggering a full build here, like in onDidChangeConfiguration
    try {
      JVMConfigurator.configureJVMs(prefs);
    } catch (CoreException e) {
      logException("Failed to configure Java Runtimes", e);
    }
  }
  logInfo("Updated preferences from initialization options");
}