C# Generator: Generate range for different formats

[rbergheim]

This is an attempt at generating C# Range annotations that supports more formats. My problem was that this property:

myProperty:
  type: integer
  format: int64
  minimum: 0

Generated this C# code:

[Newtonsoft.Json.JsonProperty("myProperty", Required = Newtonsoft.Json.Required.Always)]
[System.ComponentModel.DataAnnotations.Range(0D, double.MaxValue)]
public long MyProperty { get; set; }

The code was defaulting to using double values if the format was not int32. In my example it should use 0L, long.MaxValue. Now it should use the correct suffixes and the correct max values.

[RicoSuter]

Thanks for the PR.