Add Windows NSIS Installer

* using Modern UI 2 interface
* using named mutex to allow run only one installer instance
* support both 32 and 64 bit systems, show error message when 64 bit installer is started on 32 bit machine
* support upgrading via removing previous installation
* optionally can create startup and desktop shortcuts
* creating uninstaller and adding it to add/remove programs menu registry

* only trojita executable (without any DLL libraries) is included in installer

REVIEW: 112224