up ginac expression :
- fix x,y,z symbol : ( use only symb present in expr : 3*mu*sin(2*y):mu:y)
- up support  :  g.setParameterValues( { expr ,val  } )  and  g.evaluate( { , } ) // for only one symbol
- add new constructor which evaluate the ginac expr  : auto g = expr( expr, mapValueParam, filename )
- double res = g.evaluate() can be called thank to previous initialization
fix backend()->maxIterationsSNES()