'hydroPSO' function: argument 'method' now allows 'canonical'. 'fn' argument now can be function or character

'hydroPSO': immproved checking of some arguments; 'random.update' only used when 'best.update'=async, and more and better examples. 'text\_functions': corrected name of the 'rastringin' function, and corrected definition of the 'shafferF6' function

new 'random.update' parameter for the 'control' variable, in order to allow random update of personal/global best

hydroPSO: fixed small bug related to improper PSO evolution when 'best.update==async'. source code was tidy up. Added '...'  parameter.