add option to remove common indent from note body

[derrotebaron]

For example:

* foo
** bar
   example content
     deeper indent

will display

example content
  deeper indent

instead of

   example content
     deeper indent

as text of a note.

This does not apply to the EditText, because it might confuse the user when
typing spaces at the beginning of a line, as they wouldn't show up if they are
part of a common indent.

The reasoning behind this feature is, that indents in Emacs Org-Mode are by
default as deep as needed to match the text of the innermost subheading
that contains the body to be indented.

[nevenz]

This is when org-adapt-indentation is used?

I think this should be an option under "Settings / Sync / Org file format" and only done when parsing or writing to Org files. I don't think content should be changed within the app.

It could be detected automatically too (currently done for planning times and properties when parsing), though that might not always work.