Update the code to use the background geolocation plugin

[sergiodurand]

All the code so far was based on the geolocation plugin that only works if the application is running in the foreground. It need to be updated to use a plugin that continues working in background.

After a quick search I found the following plugin: https://github.com/mauron85/cordova-plugin-background-geolocation

Need to investigate the "battery-saving" feature. Maybe it could be a solution for the issue Reduce GPS Usage [#1].