Remove tool-specific code from project.setTool to the tool's register function.

Still pending: tool-specific code in project.destroy()
Formatted a few lines in project.js
overview.js: safer SVGOverlay.destroy method.
Timeout-free selection of a skeleton node when "URL to this view",
and perform one single repaint, not 3, of the SVGOverlay.
The first two of these repaints were for the whole section area,
potentially pulling thousands of nodes from the database.