Implemented UglifyJS directive to suppress unreferenced symbol warnings.
Work around build break because of source-map 0.1.35

Depending on https://github.com/mozilla/source-map/issues/123 it's either a bug in source-map or in TypeScript.
Implemented SimpleSet.size
Use a set to hold font URLs to avoid duplicates.
UJS.SourceMap.root defaults to null.
Don't rename "_classTag" property in minifier. webworker serializer refers to it by name.
Added default value of RendererSettings.preRenderTime to JSDoc.
Added RendererSettings.preciseOutlines

When false, outlines are rendered in increments of the gaussian blur (if any). Vastly boosts performance for large-outline-large-blur lines and doesn't look appreciably different.
Revert "Work around build break because of source-map 0.1.35"

This reverts commit 54b424548293ef35339e24cc9a6665c8a168c096.

Fixed in source-map 0.1.37.
Nested rotations.