Improve whitespaces/indentation

[Querela]

Hi,
looking through the source code was a bit of a pain with the inconsistent indentation... (Noticable when opening with code editors that assume tabs are 4 spaces which makes looking through code in diffs etc. difficult when tabs and spaces are mixed and tabs are not 4 spaces wide.)
I saw that in the majority of files the indentation was 4 spaces, so I converted or "fixed" everything I noticed.

• In particular 8 spaces seemed to be expressed as tabs which I converted to spaces. There was also a mix of tabs and whitespaces when it was not dividable by 8.
• A few files used 2 space indentation which I converted to 4.
• Any trailing whitespaces were trimmed.

I saw some alignments in function parameters and conditional expressions that I also fixed to be similar to what I saw in other places.

I did NOT run an auto-formatter, so custom indentation (in conditionals, argument lists) should have been preserved.