(Closes issue #152) : Use Snarl popups
* include the snarl API
* use snarl to show a popup if it is running, otherwise still use the CommitMonitor popup as usual
* include the png resource in the installer for snarl to use
(Closes issue #156) : Installer should remember previous install location
* save the install location in the registry and make the installer use it if available.
Fixes issue #155
Create the msi version info from the version.in file instead of relying on the developer to manually edit the wxs file for every release.