Add transaction ID to query stats for easier cross-referencing of txlog and querylog streams.
Add querylog txid to querylogz output.
Merge pull request #63 from plobsing/querylog-txlink

Add transaction ID to querylog entries.
Tweak Context representation on status pages
Pull Context out of tablet
Refactor VTGate to use Context interface

Keep last error context in EndPointsCacheStatus
Add context to GetSrvKeyspaceNames and GetSrvKeyspace
Merge branch 'master' into replication