Removed ItemNumber attribute from TaxRate\Name, Added TaxComponent 

Removed ItemNumber attribute from TaxRate.Name
Added Tax Component Model

re Xero Network & Developer API - ticket number 938544

C# wrapper was treating Tax Rate Name as an ID so the URL was being constructed incorrectly.
 
https://api.xero.com/api.xro/2.0/TaxRates/96161Truckee?Status%3d%22ACTIVE%22
 
Instead of 
 
https://api.xero.com/api.xro/2.0/TaxRates?where=Name%3d%2296161Truckee%22+and+Status%3d%22ACTIVE%22