Cleanup old refactored code
Bulk: prototype for InsertBatchedAsync() (not working yet!)

- Same as InsertAsync() but where you get batches of T[] instead of each T one by one
- Helps reduce overhead of tasks, and allows using batch-optimized insertion methods in the db
- This method does not handle failure/retries properly yet!
Tuples: optimized decoding of tuple entries, and made some changes to the encoding of DateTime / TimeSpan ...

- Rewritten decoding path with generics to be much faster, by decoding the slice directly to the wanted type, instead of calling DeserializeBoxed and then converting to the target type.
- Changed the encoding of DateTime and TimeSpan to use 64-bit floating points instead of number of Ticks (which would overflow on JavaScript anyway)
- Fixed few bugs in deserialization methods that weren't called up until now.
Tuples: refactoring/cleanup

- Moved ParseNext() method to FdbTupleParser class
- Added [NotNull] anotations
Converters: added support for converting a subclass into its baseclass

- Allows things like Convert<FdbTuple<int, int>, IFdbTuple>(...) to work