refactor code :  loop over result sets, issue #44
populate all series using a loop, issue #44
fix spacing
improve captions
use constants
Merge branch 'issue_26'
add file comment and license
fix coding style : correct indentation
move series merging to seperate function
show week, month and year data in day_of_week chart, issue #44
Display buildtime averages of different timeframes in the same chart, close #44