Partially overhauled content system's metadata handling, Fixed & Added tools, Added missing resources, Other minor fixes, Added index compiler

Update .gitignore, .htaccess, and 48 more files...

commons/strings/en/sidebar.json

@@ -7,6 +7,7 @@
   "sidebar.text.applications": "Applications",
   "sidebar.text.libraries": "Libraries",
   "sidebar.text.electronics": "Electronics",
+  "sidebar.text.3d-print": "3D Printing",
   "sidebar.text.tools": "Tools",
   "sidebar.text.links": "Links",
   "sidebar.text.downloads": "Downloads",