Add more Node.js module utilities

Tests coming soon...
Make module resolution more closely match Node

Read the source, Luke!
https://github.com/joyent/node/blob/master/lib/module.js
Steal Node's module resolution test suite

This code now works, thoroughly. :zap:
Move OpenFileInPreviewTab() to FileHelpers

TODO: Make other features call this
Add Go To Definition for Node.js require() calls
Remove extra files from project

I forgot to save the csproj earlier after deleting these files...
:frowning:
Add missing dot

Including test case
Removed debug statements and made a few fixes
Optimized CSS sync on save
Fixed issue with menu auto-hide
Menu items for Unused CSS