Improve UI

The current process for running CFSSL with a UI is inconsistent and the documentation does not match the implementation. Furthermore, some key features are missing from the UI.

• Fix documentation for the UI creation with rice: it should be easy for someone to come to the project and build the UI into the cfssl binary by following the README directions. The Docker build should also automatically build the project with UI.
• Add all missing scans results to the UI
• In the bundle UI, add the ability to drag and drop a certificate or certificate chain file to be bundled
• Add a tab for sign, that mirrors the sign API and returns a signed certificate
• Add a tab for certinfo that returns information about the certificate