[t]explorer.bitcoinabc.org is going to be retired soon.
explorer.viawallet.com has been a redirect to expplorer.coinex.com for a
while now.
Add texplorer.e.cash
Users who previously selected [t]explorer.bitcoinabc.org will switch
to using the default explorer, which is [t]explorer.e.cash
For users who selected explorer.viawallet.com this diff adds some code to
automatically switch to coinex.explorer.com.