[1/2] Base: Upgrade network traffic meter
*Updated class name to be less ambiguous
*Replaced the multi-check in settings with a proper listview
*Added the ability to view up-stream, down-stream or both
*Added the option to change how often it refreshes
*Added a check before it updates the status bar to prevent it from
refreshing everything needlessly
*Added icons to show data direction
*Remove unused style attributes

Icon artwork is courtesy android design downloads
Some features were inspired by previous work done by 0xD34D

OmniGears: https://gerrit.omnirom.org/#/c/5130/

Change-Id: I9f86292a6adbc5e30967df76fae510be248fc38b