Merge pull request #3 from typecho/master

update
重新修改上下文，兼容原来主题
Merge pull request #213 from shingchi/test

Test
fix #219
修正后台->设置->评论->允许使用的html标签里的重复编码问题
Merge branch 'master' of https://github.com/typecho/typecho
给attachment增加offset
add attachment alias
修改取附件的默认顺序，更符合通常需要
给category list增加聚焦效果
Update Db.php

修改数据库连接池实现
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