[xupdate]error recovery on Xupdate_ModulesIniDadaSet::_getItemArrFromObj

稀に X-update が起動しなくなる問題の対策（暫定）
ref. http://xoops.hypweb.net/modules/forum/index.php?topic_id=3267
[X-update] edit CSS by @xoops123

ref. http://on.fb.me/ZEYxm0 (@FaceBook)
[X-update] use extension_loaded('json') for JSON extension check
Merge branch 'xupdate' into CorePack