Fix typo in CantileverPlateTest expected result
Follow coding standard (spacing around binary operator)
Refactor Fem2Dtest defineTriangleStrips arrays not needed (consecutive indices)

the method was taking 2 arrays and using the indices in these arrays.
But we use it only with arrays containing consecutive numbers. Therefore the arrays are not necessary, only the start indices and the number of indices is necessary.
Factorize Fem2DUnitTest membranePlateWithSemiCircularHole