v3.0.0

• Split code into multiple packages, but mongoschema package still includes them all
• Added SchemaVariant!(Types...) struct which is a variant that serializes depending on the stored value and deserializes back to it.
• ints implicitly convert to longs now when reading
• added tryFind overloads which return a default value instead of nullables
• added a new query framework. You can now do typesafe searches using MySchema.findOne(query!MySchema.key1(value1).key2(value2).someInt.gte(40))