simple progress bar

[yberol]

@lileicc @cberzan

it would be useful to print how many time steps the particle filter have processed.
See displayprogress of MATLAB.

function reverseStr = displayprogress(perc,reverseStr)
msg = sprintf('%3.1f', perc);
fprintf([reverseStr, msg, '%%']);
reverseStr = repmat(sprintf('\b'), 1, length(msg)+1);
end