qt channels list: make selection more in line with other tabs
qt channels list: make selection more in line with other tabs

(allow selecting none, and allow multi-select)

wakiyamap/electrum-mona,pooler/electrum-ltc,pooler/electrum-ltc,vialectrum/vialectrum,spesmilo/electrum,spesmilo/electrum,spesmilo/electrum,vialectrum/vialectrum,wakiyamap/electrum-mona,wakiyamap/electrum-mona,spesmilo/electrum,wakiyamap/electrum-mona,pooler/electrum-ltc,vialectrum/vialectrum,pooler/electrum-ltc