Couple of multi extruder related fixes

- also recognize such temperature reports that do not contain a "T:" but a "T0:" (should help with parts of #345)
- properly parse temperature commands to track target temp during slow heatup
- for the former point, also keep track of the currently selected tool
- simulate heatup and replies without "T:" in virtual printer (to test all this)
- also auto-caps T commands in terminal