Add check invalid geometry on Layer

[avancinirodrigo]

@pedro-andrade-inpe This feature is needed to LuccME. That is possible because terralib provide a function to check.

I am thinking about to add a parameter on Layer{check = true}. Or, it can be a function as well, like layer:check().

[pedro-andrade-inpe]

I prefer a separate function, because it possibly takes time.