Provide a graphical Windows installer

This PR provides the nsis (http://nsis.sourceforge.net) script for creating a graphical Windows installer for the ODBC driver. I haven't committed the installer executable with this PR, but you can check it out here: https://github.com/nezihyigitbasi/presto-odbc/tree/binaries/binaries/64-bit. I have successfully tested the installer with Windows 7 and Windows Server 2012.