[Added] Avg daily income in bar chart and new total transactions plot

[*] Now the average daily income is drawn into to the daily income bar
diagram as a horizontal line
[*] There is a new total transactions plot, but no dates are displayed
right now
[*] Minor bugfixes to clear figure data after plotting
[Added] Filters to select mine sources that should be calculated

It's now possible to select the mine sources for the data analyzis. For
that reason the user must use the command line switch -f followed by the
labels of the data source: E.g: -f source1 source2 sourceN

This commit also enables the total transaction plotting mode, that was
implemented last time.