fix prefs.js and schemas
add .gitignore
add bitcoin logo

Source: https://en.bitcoin.it/wiki/File:BC_Logo_.png
remove log statement
move data formatting to ApiProvider

formatting is dependent on the api we fetch the data from, so it is done in the
ApiProvider
use imports.signals instead of CallbackQueue
imports reorg
use gsettings
fix docs
use gsettings signals
var declaration changes, fix destroy() methods
make refresh symbol clockwise
use more Lang.Class instead of ad-hoc classes
fix loops
initial preferences dialog
changing, adding and removing works

error when removing on empty list