removeVariable: method semantic is not really clear

[SergeStinckwich]

What is the exact purpose on this method? This is similar to substitute a variable by 1:

On a binary expression S*cos(t):

	e := KEBinaryExpression new
		     op: #*;
		     leftHandSide: (KEVariable new symbol: #S);
		     rightHandSide: (KEMathFunctionExpression new
				      functionName: #cos;
				      functionExpr: (KEVariable new symbol: #t)).
	n := e removeVariable: (KEVariable new symbol: #S).

returns cos(t).

except on a single variable:

	e := KEVariable new symbol: #S.
	n := e removeVariable: (KEVariable new symbol: #S).

n is nil is this example.

Why do we need this?

[btmanh]

I dont remember the objective of this method, if it doesnot have any usage in other classes, so we can remove it

[SergeStinckwich]

This is in fact used only in equationsToTransitions see #291 and in KEComponent>>mergeEventsWithSameActionsIn: eventList