Javatest 4.2 (should be reproducible since jt4.0)

- write custom testsuite that would use TestSuite's loggers that forwards log messages to LogViewer (View/Logs) window. See com.sun.javatest.TestSuite#createLog(WorkDirectory, String, String)
- create logger and log there several messages with different Levels: LEVEL.SEVERE, LEVEL.WARNING, LEVEL.INFO, LEVEL.FINE. Log some messages with your own "custom" Levels that may have alternative names.
- run code. Open Log Viewer.
- All submitted logs are split between 4 "private" levels of the LogViewer:
* Debug Info
* Monitoring Info
* Warning
* Critical

This was the initial design of the Log Viewer. However now it's obvious it's wrong to replace Level's, submitted as part of LogRecord's with these artificial strings.

This RFE for LogViewer is to use 'Level' objects from submitted records to show and filter information.
This may be combined with some redesign of the LogViewer UI, or, as the easy solution, UI may stay the same but filtering "checkboxes" should be updated in runtime according to submitted log records.