Minor updates and improvements

Replaced ElementLocator Evaluate method by Format method
Replaced DriverContext.BrowserType by BrowserType
Set PageLoadTimeout, ScriptTimeout, ImplicitlyWait timeouts for Driver
Added GetUrlValue and GetUrlValueWithUserCredentials to the BaseConfiguration
Updated Selenium version to 2.50.1
Updated SpecFlow to official version 2.0.0
Updated ChromeDriver to version 2.21, IEDriver to 2.49
Added missing references System.XML, System.XML.Linq
Updated api documentation http://objectivitybss.github.io/Test.Automation
Symbols publish on www.symbolsource.org - possibility of debugging our Test.Automation
framework, more details here.

Support for xUNIT test framework

Added xunit test framework,
Added wait for angular method to check pending angular requests,
Added WaitHelper, WaitTimeoutException classes for handling wait with timeout