Debugger: Remove unused 'precise breakpoints' setting.

Remove break window menu action to toggle 'Full path'.
Remove gdb setting 'Use full path'.
Clean up break dialog:
- Set PathChooser::ExpectedKind before value (showed up in red).
- Use PathChooser::setPath()/path() instead of lineedit text
- Return thread spec
- Add validator for ignorecount as for breakcondition.ui
Remove unused fields from breakcondition.ui

Reviewed-by: hjk
Task-number: QTCREATORBUG-2593