Continuing to flesh out the navbar editing functionality.
Added a login form template and reconfigured the package to use the flask login manager.
Finalized the changes to the first revision of the navbar modules.  TODO: make this its own package with extensible edit engine.
Fixed document DTD, moved right bracket template to top-level layout.
Added a uniqueness constraint on the id column of the nav table.
Added stubs for an install script and login page to the view functions.