Fix undefined electrumServers

[sawlysawly]

Fixes #205

[pbca26]

unfortunately we already had quite a handful of issues with global
it's better to use ipc for any large collections of static data

please don't submit PR to master branch
the process is dev -> master

[sawlysawly]

ok I will submit to dev for more PR in future thanks

for this issue #205 it still needs to be fixed

this PR is fixes the issue but i agreed its not good to add lots of stuff to global

I think then the issue is in util/mainWindow.js. it refers to the global value but it doesnt exists

@pbca26 can you refer to #205 for more informations