New directory browser.

Instead of using the ugly Windows95-esq built in folder browse WIX
dialog, the DLL will use a .NET dialog instead. Since the CustomAction
is setting the INSTALLDIR property, and you cannot "refresh" dialogs in
WIX, I had to duplicate the CustomInstallDirDlg and have them alternate
between each other every time the user changes the installation
directory.

SetupMSI will use the appropriate files now (Debug/Release).