Begin of new concept: rendering Topics as HTML.

This is in experimental stage. There is a new branch "topic-html".
Not fully usable.

Works in conjunction with the DeepaMehta "topic-html" branch.
Adapt to current DM Webclient.

div#canvas-panel -> div#topicmap-panel
Extend HTML based rendering.

The topic's mini icons are shown.
Adjust HTML/CSS when updating topics.
HTML rendering: hiding/deleting/create assocs.

- Hiding and deleting topics works.
- Creating associations works (both, via content menu and via mini icon).
Split project into 2 Canvas/HTML sub projects.

The former dm4-box-renderer is now at:
    https://github.com/jri/dm4-box-renderer-canvas

The new HTML based version of the Box Renderer:
    https://github.com/jri/dm4-box-renderer-html