adding new analysis function (combined stdev/mean)

main
- added option for appended stdev and mean of combined speed
measurements

STDS
- made progressBarLen a class variable

SpeedTestFile
- added function calc_TCP_Total_StDev_and_Mean_then_Append()
- added import of calcMean() for use by new function

TCP_Test
- updated function calls

Ping_Test
- As the test number is always in the text passed to the constructor,
that class variable is always parsed and declared

utils
- renamed StDevP to calcStDevP
- created calcMean. takes an array like calcStDevP
- calcStDevP uses calcMean