Statusbar: Add network speed indicator, (1/2)

Base network speed indicator is ported from ThinkingBridge:

https://github.com/ThinkingBridge/platform_frameworks_base/commit/06ea69be759fa68cbb2fd0d7616d48f5ba485954

Included:

- Indicator for download speed
- Indicator for upload speed
- Show values in bits or bytes
- Hide indicator while there is no data traffic
- Download speed indicator color
- Upload speed indicator color