[C#] Extension to allow Read of all versions of key in FasterKV log

[TedHartMS]

• Add IAdvancedFunctions, which adds parameters to IFunctions methods:
  • ReadCompletionCallback has an additional RecordInfo parameter
  • Reader/Writer methods have a logicalAddress parameter
• Add AdvancedClientSession, which is a parallel (not inheriting) class to ClientSession that takes an IAdvancedFunctions instance
• Add AdvancedFunctionsBase and AdvancedSimpleFunctions
• Add a DEBUG-only IClientSession interface to ensure the Session classes are consistent
• Add overloads of Read() and ReadAsync() that take a starting address that is used instead of a hash table lookup (traceback for key match is still done), and returns a copy of a found record's RecordInfo whose PreviousAddress can be passed to the next iteration of Read() to trace back a key's records. This requires IAdvancedFunctions and AdvancedClientSession
• Add ReadAtAddress and ReadAtAddressAsync to read from an address when there is no key available (the key is passed to the IFunctions or IAdvancedFunctions Read methods)