nanoDLP

After direct experience of the problem due to an excessive current consumption on 5V rail from external device, I realized that could be useful (both for debugging and for process integrity) if NanoDLP could detect ramps failure (not responding or reset), pause the print and warn the user.
Reset detection should be easy enough (looking for "start" keyword from RAMPS).

Also I think it would be better to wait for "ok" response after each command before issuing the following one. This way printing will stall if something goes wrong and dashboard status info would actually be useful.
Right now, when there is some problem with RAMPS connection, print execution continues at least till the next "WaitForDoneMessage".