Insert new MNIST example program from the Chinese README.md into the English version

Polishing sentiment role labeling using paid Grammeraly

Add .DS_Store into .gitignore

Semantic labeling tutorial data and code section in English.

Update build.sh and update all html files

1st round chapter 8

Use English figures in all README.en.md files

added figure 5 translation in chapter 4

update mnist doc

1st round translation of Chapter 6

Update the label_semantic_roles doc.