Introduced a mechanism to load required javascripts at runtime

(lazy loading) using the require.js. This allows us to load the
javascript required for any node, only when it was loaded in the browser
tree. Also, introduced the mechanism to show/edit/create of any node in
a tab panel (wcDocker.Panel).

.gitignore

@@ -14,3 +14,4 @@ runtime/pgAdmin4.app/
 runtime/pgAdmin4.pro.user*
 runtime/ui_BrowserWindow.h
 web/config_local.py
+web/pgadmin4.log