BCL proxies updated for #450.
Issue 504 partial fix.
Merge pull request #562 from iskiselev/Issue504_Partial

Issue 504 partial fix.
Delegate/lambda tests added.
Merge pull request #557 from iskiselev/BclProxies450

BCL proxies updated
Implemented  XmlReader methods: MoveToNextAttribute, MoveToElement; props: HasAttributes, Prefix.