Indentation fix.

Fixed the inconsistent indentation to 4 spaces in almost all files. Some were using tab-size:4. 
(Not a huge issue, but the inconsistency did show some ambiguity when reading code)

While this certainly shouldn't break any part of SET, you can git-pull the 'cleanup' branch into another local branch if you wish to test/review the commit instead of merging directly to master. :smiley: