Move documentation on tool changes from wiki

Move documentation on tool changes from wiki

Move the text on tool changes from the wiki page to the user guide,
where it is much easier to maintain together with the code changes.
For now, this only contains the 5.0-era changes more or less directly
from the wiki, but I will improve this (as a separate change) once I
have more time.

Change-Id: I4ccea605783de2949221d604e232b36c726dcaa7