Indentation actions need big polish

[joaomoreno]

Testing #3234

I'm having trouble understanding how to use the indentation actions:

• Indent using Spaces
• Indent using Tabs

They seem to change how the editor will insert indents from that point forward, without changing the indentation of the content already inside the editor. Not only can this produce mixed indentation files easily but it's only half way to the most common use case: change the file's indentation from one mode to another.

They also seem to produce no visible changes to the editor. Especially if you have a file already indented with tabs, choose Indent using Tabs and select a different tab width than the currently configured one, nothing happens. The file shouldn't change, but the view should adjust to the new tab width.

I suggest to replace both actions with a single Change Indentation Size.