Improved extended information serialization, changed Minidump write for normal type

Since MiniDumpType Normal always throws exception and Tiny/Full modes are working fine, seems to me problem is in DumpTypeFlags specified, not process/resource locking. I've commented existing code, replaced it with single flag, tested it (with and without debugger attached) and works as it's supposed to.

I've found many values in SerializableDictionary causes NBug to crash when trying to write with XMLWriter, even when type supports serialization. Since we're talking about extended information it seemed to me the most important thing is to report what-we-have, and provide ToString for everything we cannot serialize.

Also, there is bug with LINQ call.