Proposed updates to smokeping RRD rendering

Hi there,

Please excuse any mistakes Ive made in logging this request, I'm not very familiar with this project or Jira general practises.

Ive made some modifications to my obs instance;

• fix average / red line dropping to zero at the right end of the graph
• colour the average line based on packet loss threshold
• colour the background based on packet loss threshold
• draw packet loss thresholds on legend
• annotate legend with number of probes/interval etc
• updated loss average for period to display with 3 decimal places 

All changes are within this file "./observium/html/includes/graphs/device/smokeping_all_common_avg.inc.php" and I have attached my new/modified version of the file with comments

I was hoping this could be reviewed and possibly integrated into mainline to enhance for all users using smokeping integration

Cheers,

Matt