windows/msi: enhancements to installer

This starts from contributed https://github.com/joyent/node/pull/4420 and https://github.com/joyent/node/pull/2948 and adds some additional enhancements and fixes.

Noteworthy improvements provided by the series:
* Support in the Installer UI for not installing shortcuts.
* Support in the Installer UI for choosing a custom install directory.
* Command line support for not installing shortcuts (ADDDEFAULT=nodejs)
* Command line support for custom install directory (INSTALLDIR=c:\tools\node)
* Placing Node's install location in the registry both to help other apps find node.exe and for future installations to be installed over the same place.