Apply changes after third HW rewiew.

[RobertGawron]

Chosen PMT needs 1k5V, much more than originally planed, using cascode with transistors in series seems to be a bad idea.

Use shunt voltage regulator for first winding of transformer, this will keep regulator-transistor voltage small. High voltage wil be build by connecting transformers winding in series. This will also solve problem with finding diodes with sufficient reverse voltage.