Use unified Error and Warning handlers, rather than console.error and console.warn

In https://Clara.io, we need to know if any errors or warnings happen within ThreeJS.  Right now most errors and warnings are piped to the console.  This isn't useful for us.  So in our version of Three.JS we have created centralized THREE.error and THREE.warning functions that are used instead of writing to console.log/error/warn that are optionally redirectable.

This allowed us to identify a number of bad behavior in our code.  We love this functionality and the default error and warning handlers output to console.error and console.warn respectively, so this doesn't change default behavior, just adds flexibility.