Modernize Select2 integration and fix popover page jumping

- Upgraded Select2 from bundled v3.4.4 (2013) to v4.x peer dependency
- Removed legacy Select2 v3.x bundled files from lib directory
- Updated Select2 input to use v4.x API (events, AJAX, templates)
- Fixed Bootstrap 5 popover page jumping issue with multi-timeout scroll restoration
- Added comprehensive migration documentation in README-select2-upgrade.md
- Rebuilt all distribution files with updated source code

Breaking Changes:
- Select2 now requires separate installation as peer dependency
- AJAX configuration updated for v4.x format
- Event names changed (select2:select vs select2-loaded)
- Template functions renamed (templateResult vs formatResult)

Gruntfile.js

@@ -268,7 +268,8 @@ module.exports = function(grunt) {
         evil: false,
         globals: {
             jQuery: true,
-            console: true
+            console: true,
+            bootstrap: true
         },  
       },
       js: [   'Gruntfile.js',