Problem:
Test-cases history are displayed incorrectly after multiply update.

Description:
(I have attached update.zip file with .csv files and screenshots)
- Prepare few different test-cases in csv format. (before_update.csv)
- import them to projector using Import Data feature: (before update.png)
   -'element type to import' - 'test case'
   -'file format to import' - 'csv file (comma separated values'
   -'file' - 'before_update.csv'
- see into history for each test-case (there is only 'insert' operation)
- perform some changes for existing test-cases (prepared_for_update.csv)
- import changed test-cases to update existing in projector (upd_process.png)
   -'element type to import' - 'test case'
   -'file format to import' - 'csv file (comma separated values'
   -'file' - 'prepared_for_update.csv'
- navigate to properties of each test-case (1130 history after update.png, 1131 history after update.png, 1134 history after update.png, 1135 history after update.png)

RESULT: information about update is the same for all test-cases in the "value before" field. It is the same as for the first test-case. Only first test-case 1130 has correct information in history (1130 history after update.png)
