[0.4.5] "Zip" functionality and change-able backends

This release introduces two new features:

1. Changing backend with Iobeam.Builder.setBackend(backend)

2. "Zip" field names and data points. If you have a list of fields and list of datapoints, you can now
   have them sorted correctly in the datastore with one method:

String[] seriesNames = {"series1", "series2", "series3"};
DataPoint[] datapoints = {
    new DataPoint(1000, 2000),
    new DataPoint(2000, 3000),
    new DataPoint(3000, 4000)
};
Iobeam iobeam = getBuilder().build();
iobeam.addDataMapToSeries(seriesNames, datapoints);
// DataPoint(1000, 2000) now in 'series1', etc