Added Uuid64 and renamed Uuid to Uuid128

- the new Uuid64 store a 64-bit, using big-endian ordering (there is not real standard for these)
- Uuid128 still stores a 128-bit using the RFC422 standard (as before)
- Renamed all ToUuid()/FromUuid() into ToUuid128()/FromUuid128(), and added the corresponding ToUuid64()/FromUuid64()
- Added support for Uuid64 in Slices, converters, tuples, ...
- Added unofficial 0x31 prefix in tuple encoding to store 64-bit UUIDs
- Fixed bug when converting a Guid into a bool
Added unit test to track a memory leak in fdb_c when a transaction retries
Memory Store: Added failing unit test to track bug in ColaRangeDictionary
Fixed : PrettyPrint()

PrettyPrintMode.Begin really needs to remove last byte from slice before calling unpack()
If unpack() fails, expection is catched.
Uuid64 : added a few operators (==, >=, +, ...) and more unit tests