Suggest --guess-bonds if no matching bond/angle was found in selection

[Luthaf]

Maybe only if there are no bonds in the topology

[Luthaf]

If someone is interested in implementing this, the error message to change are:

cfiles/src/commands/Angles.cpp

Lines 103 to 105 in 464a0ca

	warn_once(
	"No angle corresponding to '" + selection_.string() + "' found."
	);

cfiles/src/commands/Rdf.cpp

Lines 225 to 227 in 630f70e

	warn_once(
	"No pair corresponding to '" + selection_.string() + "' found."
	);