Contact position is inconvenient after changing the render type

[Danil Sokolov]

To reproduce:
 - In digital circuit model create a function block with A+B+C+D set function.
 - Change the render type to GATE, then to BOX, and then to GATE again.

Observed behaviour:
 - The contacts stay in the positions of the BOX and there is no simple way to set them into GATE default positions.

Expected behaviour:
 - The position needs to return to default state of the particular render style, if not at once, then by "Set default contact position" pop-up menu.