Added GUI, Search and Add User

I added a page at the root that displays the local packages and allows users to search through them.  The page shows basic information about each package including its name, author, description and README.  I also added the capability to add users from the command line.  This involved removing user configuration from the config.yaml and using a users.json file that is written only by the Sinopia server.

This is a large set of changes that will require some additional work before merging.  However, I wanted to get the process started to make sure that the new code is on track.  Things that still need to be changed:
- Add tests for new functionality
- Add instructions for development.  (How are you compiling the package.yaml to json for installs?)
- Add user permissions to the new user model

Thanks for your help and hopefully we can get this code integrated into the project!