when Darksend is unchecked select nondenom inputs first - for v0.11.0.x

Select "regular" funds first when user unchecked "Darksend" checkbox on "Send" tab (function SelectCoinsMinConf is used only in that case right now). This should help to preserve already anonymized funds.
PR for v0.10.17.x https://github.com/darkcoin/darkcoin/pull/78