Initial Stave implementation

This initial release contains the basic visualization components, a minimal user management system for team annotation, and a prototyped plug-in system, the details include:

1. Basic Span Link visualizer for forte data packs.
   a. Spans visualized as highlighted and bracketed text.
   b. Links visualized as lines between spans.
   c. Scope selector to allow the viewer to focus on one particular annotation type.
   d. Legend to show the color of each span.
   e. The annotation information box to show the information of the annotation.
2. Basic data edit functions.
   a. Span annotation as highlighting a span, or clicking the begin and end of the text.
   b. Link annotation by drag and drop using the small + sign on the span corner.
   c. Group annotation by adding elements into the Group plugin
3. Two example plugins: Group viewer and DialogueBox.
4. A database structure that manages documents as project, and user permission on the project level.
5. A sample Job system that tracks whether a document is finished.
6. A configuration system that can change what interfaces are used.
7. Project and User panel for the basic project and user management.