Label Support, Improved Scrolling and Bug Fixes

New Features & Improvements

• Add support for labels #1152
• Isolate Chosen Scrolling #1155

Bug Fixes & Refactoring

• Fixes bug with Isolated Scrolling #1186
• Remove unused get_side_border_padding #1169
• Fix issue when using both jQuery & Prototype #1168
• Fix choices_click method #1163
• Fix Right-to-Left scrollbar issue #1159