Change CouchException to include the request URI

This way it will be easier to debug exceptions when they happen in production servers.
Fix bug in ViewOptions which check the wrong keys length.

The property isAtKeysSizeLimit always check the ToString of Keys which return CLR type name.
Thanks to Ian1971 we fix the bug and now checking the actual keys string.
Also increase the keys length limit to 6k.
Merge pull request #54 from teci/DetailedExcpetion

Detailed exception and keys length limit