Generate Model Function GetAll filters fix

[cdavid14]

1. If you use filter expr "isnull" you should use a boolean value, as the filters and values are queried as a map[string]string object, then i added a if condition to fix this
2. If you use filter expr "in" you should pass a array of content splitted by comma, so i've just splitted the string using this delimiter and passed as arguments on Filter function.

[cdavid14]

@flycash please review :D