hough_circles: enable to set double value to the HoughCircle params

[k-okada]

current implementation takes int value for parameter of hough circle detection, but opencv hough circle support double value
http://docs.opencv.org/2.4/modules/imgproc/doc/feature_detection.html#houghcircles

C++: void HoughCircles(InputArray image, OutputArray circles, int method, double dp, double minDist, double param1=100, double param2=100, int minRadius=0, int maxRadius=0 )¶

• hough_circles: fix default/min/max value of cfg
• hough_circle: enable to set db to 100
• circle_hough: dp, accumrate_threshold, canny_threshold is double, not int