Merge pull request #222 from loftor-git/master

Update Db.php
fix typo
fix #217
close #227

修正在检查重写时无法保存链接样式的bug
fix #226
disable curl https verify
add constant to disable theme file writing
add __TYPECHO_UPLOAD_ROOT_DIR__, __TYPECHO_UPLOAD_PREFIX_URL__ constants
add default query setting method
add __TYPECHO_THEME_URL__ and __TYPECHO_PLUGIN_URL__ constants
add __TYPECHO_SITE_URL__ constant
change __TYPECHO_UPLOAD_PREFIX_URL__ to __TYPECHO_UPLOAD_URL__
disable first user delete
add widget dynamic alias method, which allows you hack widget class anywhere
fix some bugs
clean some unused widgets