Make histogram y-axis formatting aware of the tick size when formatting

kbn.byteFormat & kbn.shortFormat take an extra min_resolution param that indicates what size should be still be distinguishable despite the formating. For example if `min_resolution=100` and we fromat 1100 with `decimals=0`, the output will still be 1.1K . This is used in y_axis formatting to make sure the legends are able to correctly display a change of the current tick size.
Merge remote-tracking branch 'bleskes/y_format_sensitive_to_tick_size' into boaz
refresh was called twice with every timer expiry

Also unpacked  dashboard.set_interval to simplify logic a bit.

Note: set_interval used to call refresh() when called. This is un-expected when setting a long refresh interval.
Merge remote-tracking branch 'bleskes/double_refresh' into boaz