Isolation Forest for anomaly detection

[rayeaster]

Isolation Forest is useful algorithm in anomaly detection, low processing time and low memory footprint:

paper: https://cs.nju.edu.cn/zhouzh/zhouzh.files/publication/icdm08b.pdf

reference implementation in Matlab by paper author: https://github.com/zhuye88/iForest

[conquer66666]

please add the new feature,its usefull

[haifengl]

added