完善bst文件

修改bst文件，添加如下功能：
1. 添加对英文文献title的自动大小写转换；
2. 去掉自动加“Proceedings of”的功能，因为绝大多数bibtex都会自带它；
3. 添加对本科学位论文支持。
<a href='#crh-start'></a><a href='#crh-data-%7B%22processed%22%3A%20%5B%22https%3A//github.com/xueruini/thuthesis/pull/82%23discussion_r20479762%22%2C%20%22https%3A//github.com/xueruini/thuthesis/pull/82%23discussion_r20482033%22%2C%20%22https%3A//github.com/xueruini/thuthesis/pull/82%23discussion_r20482486%22%5D%2C%20%22comments%22%3A%20%7B%22Pull%2029b19715b354bb3d67917b5fdfa709b1d2b9aa19%20latex/thubib.bst%2016%22%3A%20%7B%22html_url%22%3A%20%22https%3A//github.com/xueruini/thuthesis/pull/82%23discussion_r20479762%22%2C%20%22comments%22%3A%20%5B%7B%22body%22%3A%20%22two%20booktitles%3F%22%2C%20%22created_at%22%3A%20%222014-11-18T01%3A20%3A05Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/1863%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/xueruini%22%7D%7D%2C%20%7B%22body%22%3A%20%22This%20is%20an%20if-else%20clause%2C%20these%20two%20lines%20lies%20in%20if%20and%20else%20branch%20respectively.%20%5Cr%5Cn%5Cr%5CnI%27m%20not%20familiar%20with%20the%20bst%20grammar%2C%20maybe%20you%20can%20rewrite%20it%20in%20a%20cleaner%20form.%22%2C%20%22created_at%22%3A%20%222014-11-18T02%3A31%3A01Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/4365070%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/pengli09%22%7D%7D%2C%20%7B%22body%22%3A%20%22I%20even%20forgot%20the%20strange%20bst%20syntax.%22%2C%20%22created_at%22%3A%20%222014-11-18T02%3A43%3A46Z%22%2C%20%22user%22%3A%20%7B%22avatar_url%22%3A%20%22https%3A//avatars.githubusercontent.com/u/1863%3Fv%3D3%22%2C%20%22html_url%22%3A%20%22https%3A//github.com/xueruini%22%7D%7D%5D%2C%20%22title%22%3A%20%22File%3A%20latex/thubib.bst%3AL573-587%22%7D%7D%7D'></a>
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- [ ] <a href='#crh-comment-Pull 29b19715b354bb3d67917b5fdfa709b1d2b9aa19 latex/thubib.bst 16'></a> <img src='http://www.codereviewhub.com/site/github-remaining.png' height=16 width=60>&nbsp;<b><a href='https://github.com/xueruini/thuthesis/pull/82#discussion_r20479762'>File: latex/thubib.bst:L573-587</a></b>
- <a href='https://github.com/xueruini'><img border=0 src='https://avatars.githubusercontent.com/u/1863?v=3' height=16 width=16'></a> two booktitles?
- <a href='https://github.com/pengli09'><img border=0 src='https://avatars.githubusercontent.com/u/4365070?v=3' height=16 width=16'></a> This is an if-else clause, these two lines lies in if and else branch respectively.
I'm not familiar with the bst grammar, maybe you can rewrite it in a cleaner form.
- <a href='https://github.com/xueruini'><img border=0 src='https://avatars.githubusercontent.com/u/1863?v=3' height=16 width=16'></a> I even forgot the strange bst syntax.


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