GDOS: Minor bugfixes and improvements

[tomas-nestorovic]

Here should come anything on GDOS implementation that doesn't regard big new features and doesn't regard critical bug fixes. Instead, this issue should focus on the following minor changes to the source code for which it's not worth creating a separate issue:

• source code readability improvements (indenting, formatting, etc.),
• commentary improvements (typos, English, clarity, etc.)
• syntax improvements,
• etc.