Automating some WiX testing

Done:

 - logging is back to good now that I found the stupid error past me made
 - when reinstalling, you've got nothing to do - so don't throw an error
 - some tracing around WiX events for testing in an automated way
 - pushed some messages out to debug

TODO: 

 - [x] automate a test which "reinstalls" an app
 - [x] automate a test which "upgrades" an app
 - [x] automate a test which "uninstalls" an app
 - [x] tests that installer can be used with a custom folder