converted to python3
minor fix
fixed for Windows OS
fixed loop by years, removed empty data intervals on the plot
displayed graph for period of years
fixed graph
fixed cache mode
more fixes
small refactoring
fixed problem with NaN values in spread
added saving of final chart array
saved chart in file
fixed unavailability to skip empty data
small refactoring
small refactoring
added one more script argument - contract
fixed loading contracts that have been requested in arguments
saved drawdown array in file