Page management improvement and new theme

What's new:

• Now we can rearrange the page and subpage order easily. Simply drag and drop it
• New theme added to the package. Based on Doks theme by Hyas
• Automatically include the functions.php if this file exist in theme folder
• And many more small improvements

Note:

• For Doks theme. The top menu, generated from menu editor. And the sidebar menu automatically generated using get_menu function
• When naming the function in theme functions.php, use themeName_functionName(), to make sure not conflicted with existing function

Full Changelog: v2.9.0...v2.9.1