Add an attribute to the ProxyModelAttribute for using mvvmCross MvxLang

[Dexyon]

In the current version a text is a static variable

[ProxyModelAttribute(Description = "Name", Order = 1 )]
public string Name { get; set; }

In the next version we would like to have the opportunity to pass a value that is used for the MvxLang
[ProxyModelAttribute(MvxLangProperty = "Name", Order = 1 )]
public string Name { get; set; }