Fort chain undo state test, fix bug, etc.

1. add undo state tests, #68, fix a bug of update active_delegate_list_id
2. not pass every time yet. sometimes pass, sometimes fail:
```
push block: 1    my length: 24  your_length: 23 
948486ms th_a       chain_database.cpp:277        store_and_index      ]            we already know about its previous: e5a0687e8045f5aa8d4b58421441559a8b59b3e9
push block: 23    my length: 24  your_length: 23 
948565ms th_a       chain_database_tests.cpp:680  test_method          ] assert
!record: my chain's state after 5th block should have already be undo {"id":357,"name":"mytest-name-6","json_data":"6","owner_key":"0331989decea6a4f50d3e1f4f048c963588dec46e77faaedfb545ed665f0bbe88d","active_key":"02a5fe50dea041299f9965beaeb1637c2d148bcd38b3c5cac4f82247bd43903710","delegate_info":null,"registration_date":"20140523T211605","last_update":"20140523T211605"}
    {"r":{"id":357,"name":"mytest-name-6","json_data":"6","owner_key":"0331989decea6a4f50d3e1f4f048c963588dec46e77faaedfb545ed665f0bbe88d","active_key":"02a5fe50dea041299f9965beaeb1637c2d148bcd38b3c5cac4f82247bd43903710","delegate_info":null,"registration_date":"20140523T211605","last_update":"20140523T211605"}}
    th_a  chain_database_tests.cpp:673 test_method
```