MN/SN creation dialog - Coin control

[BernardCornfeld]

When creating a MN/SN via the qt dialog the needed coins are not selected with respect to the settings made via "coin control".

It would be helpful to be able to use coin control also for the MN/SN creation dialog.

An alternative would be that the dialog at least selects the coins such that the resulting tx does not get too big.

[walkjivefly]

Even selecting the largest UTXOs first might not be sufficient to prevent MN txns from getting too large (250k size limit is ~1666 UTXOs), but it would probably cover SNs OK.