Refactor data rate recording into dedicated object
Corrected method signature
Data rate recorder moved to main view controller
Display the data rate on the GCS Map View
Introduce data rate sparkling to GCS Map header view
Limit the sparkline duration to a shorter period

 - 10 seconds currently
Refined layout of header right-side labels and sparkline
Use clear colour for background

 - due to translucency of header on iOS6
Merge branch 'master' into igcs-87-comms-rate-header
Addressing review comments
Addressed review comment
Merge pull request #53 from fightingwalrus/igcs-87-comms-rate-header

Igcs 87 comms rate header