#154 bug fixes and new GC

[Da Feng]

1.There is a bug related with address base hashing.
2.Generational mark swap (GenMW) improves mark compact algorithm. It also takes into consideration more practical problems, like java.lang.Reference and referent processing, some additional objects that VM needs during processing, and difficulty of getting object start reference after moving into target region under condition of continuous layout of object on heap. GenMW stores sum of live object size into region header, and sorts region list after marking. Collector select a subset of regions from the region list, and does garbage collection on that list. One temporary region is set aside to implement swapping.
3. The readme.html file provide introduction into GenMW details.

[Da Feng]

contributor agreement

[Da Feng]

new-gc.patch, GenMW

[Da Feng]

hashcode-bug.patch

[Da Feng]

GenMW introduction

[Da Feng]

update readme.html, remove typo and wrong description