Add image features. Add repeat detection to save tokens

[ccetaw]

实现以下功能：

1. 在本地保存 实验/结果 (Experiments, Evaluation, Results...) 之前的图片， 并添加到summary最后
2. 支持非精确匹配关键词，使用--coarse激活
3. 避免重复下载分析同名论文以减少token的使用，使用--repeat来强制summarize
4. 现在总是会覆盖同名.md文件

改动集中在 get_paper_from_pdf.py中的get_image_path(self, image_path='') 和chat_paper.py的download_pdf()部分.

I've implemented the followin features:

1. Could now save images on local device and add them to the end of generated markdown files
2. Support non-exact key word matching, use --coarse to activate
3. Now the program avoids download and summarize already downloaded paper to save your tokens, use --repeat to force downloading and summarizing
4. Always overwrite the generated markdown files.

The changes mainly happen in get_paper_from_pdf.py function get_image_path() and chat_paper.py function download_pdf()

[ccetaw]

已知的bug:

1. PDF里可能包含未显示的图片，或者一个图片有多个图层，这样提取出来的图片会非常混乱
2. 生成的.md文件可能会有很多indent

Known bugs:

1. A PDF file may contain images not showed, or one image is actually composed of multiple images. After extraction it would be a mess
2. Many indents might be added to the .md files with unknown reasons

[thusjr]

加油