Add KeyStorageFlags property in CertificateConfig

Add KeyStorageFlags property in CertificateConfig to used by the
CertificateManager to instantiate the X509Certificate2
added the support of keyStorageFlags for the security configuration node
tried to implement BufferSegmentReader
fixed an exception that the socket session has been closed when sending data
tried to implement BufferSegmentReader
removed the support of .NET 3.5
appended changes for .NET 4.5 projects
added comments
improved the buffer segment reader
added more classes for CountSpliterReceiveFilter
added total length property to BufferSegmentReader
fixed lots of building errors in QuickStart because of the SuperSocket interface changes
renamed ReceiveCache to BufferList; and add Take method to BufferSegmentReader
renamed BufferSegmentReader to BufferListReader; renamed BufferSegmentStream to BufferListStream;
changed the QuickStart because of ProtoBase's changes
renamed RawPackageInfo to BufferedPackageInfo
added the IDisposible interface for the AppDomainBootstrap
replaced  *RequestInfo with *PackageInfo; and allow commands' keys are generic;