modify code to suppress or fix warnings in gcc and clang (#41)

* first fix to start branch PR

* explicit conversion from sizet to int

* Array.h and DiagonalMatrix.h

* many sizet to int conversions

* removed some unused variables and added expl overrides

* removed many unused parameters

* more typing

* even more

* last of the easy changes

OndselSolver/VelICSolver.cpp

@@ -40,7 +40,7 @@ void VelICSolver::assignEquationNumbers()
 		con->iG = eqnNo;
 		eqnNo += 1;
 	}
-	auto lastEqnNo = eqnNo - 1;
+	//auto lastEqnNo = eqnNo - 1;
 	nEqns = eqnNo;	//C++ uses index 0.
 	n = nEqns;
 }