[AC-1358] iOS: TiUIWebview - Base64-encoded credentials contain linebreaks

Problem The WebView component called [setBasicAuthentication](http://docs.appcelerator.com/titanium/3.0/#!/api/Titanium.UI.WebView-method-setBasicAuthentication). This attempts to set the Authorization header on any requests initialized by setting the url property. Depending on the length of the username and password, the resulting base64-encoded value may have line breaks. Line breaks are not allowed in HTTP headers so everything following is truncated, of course causing authentication to fail. The line breaks need to be removed before setting to the Authorization header. I assume this is also an issue on the HTTP Client on iOS, but I haven't checked. Test case 1. Use setBasicAuthentication to set a username and password for a WebView request; set the username and password to something longer than 30 characters each. 2. Set a breakpoint at about line 184 in TiUIWebView.m and inspect the value of basicCredentials before it is set to the Authorization header. 3. The value should have no line breaks to ensure the entire value is received by the server. But, if the username/password combination was long enough, it will have line breaks.