StreamId is now string in code.
Attempt to fix dialects to work with string based stream ids
Limit StreamID to 253 chars in Firebird as this is max size for default page size (4KB)
StreamId is stored as a Sha1 hash and the original stream id is stored in StreamIdOriginal in the Commits table.
Include StreamIdOriginal when selecting streams for snapshotting and remove the StreamId paramater
Merge pull request #218 from damianh/StreamStringIds

StreamIds are string based.