Update index.md

Add "API Documentation" topic
Create copy_javadoc_to_docs.rb

Copy over the JavaDoc for all projects to api/java, which is used for the documentation HTML.
Merge pull request #232 from PasaLab/master

Add a section to the Documentation HTML
update README.md in docs
rename folder from main to core
update .gitignore
clean
tune the ui
Merge branch 'master' of github.com:amplab/tachyon
update gitignore