setup.py: add 'gui' extra. potentially build Qt icons files (#4647)
setup.py: add 'gui' extra. potentially build Qt icons files (#4647)


spesmilo/electrum,asfin/electrum,pooler/electrum-ltc,fujicoin/electrum-fjc,vialectrum/vialectrum,asfin/electrum,spesmilo/electrum,spesmilo/electrum,wakiyamap/electrum-mona,fujicoin/electrum-fjc,spesmilo/electrum,vialectrum/vialectrum,wakiyamap/electrum-mona,neocogent/electrum,neocogent/electrum,cryptapus/electrum,wakiyamap/electrum-mona,cryptapus/electrum,wakiyamap/electrum-mona,vialectrum/vialectrum,pooler/electrum-ltc,asfin/electrum,fujicoin/electrum-fjc,neocogent/electrum,pooler/electrum-ltc,pooler/electrum-ltc,cryptapus/electrum