remove extra symlinks from web/ and build/web/

Remove symlinkes from `web/` and `build/web/` (excluding the top packages folder). This was creating giant (500MB) archive files of the build, and I believe causing Dartium to take a very long time to start up.

@ussuri 
Before looking at the implementation, _deSymlink sounded to me like it would replace every symlink with its linked contents. Maybe _removeSymlinks?