Fix indentation for 'Move class to File' function

'Move class to File' function did always use tab as indentation
character. As space user you always had to convert the tabs to spaces by
hand afterwards. This fix tries to find and set the right indentation
character. If no indentation character is found, it falls back to tab.
Merge pull request #366 from sven-n/fix-move-class

Fix indentation for 'Move class to File' function