Code optimization.
Track the current deleting file in sbCommonUtils.removeDirSafety().
Fix: do not remove the file if sbCommonUtils.writeFile() meets an error.
Fix: do not remove the original file if there is error overwriting a sub-page.
Fix: if the page is shortened, saving it causes excess chars left appended.
Update version info.
Merge branch 'hotfix-1.12.0a20'