Meta tags beta, sharding by tags, new importer (bigtable!), response stats, memory-idx write queue and many fixes

breaking changes

• as of v0.12.0-404-gc7715cb2 we clean up poorly formatted graphite metrics better. To the extent that they have previously worked, queries may need some adjusting
  #1435
• version v0.12.0-96-g998933c3 introduces config options for the cassandra/scylladb index table names.
  The default settings and schemas match the previous behavior, but people who have customized the schema-idx template files
  should know that we now no longer only expand the keyspace (and assume a hardcoded table name).
  Now both the schema_table and schema_archive_table sections in the template name should have 2 %s sections which will be
  expanded to the keyspace and table, or keyspace and archive-table settings respectively configured under cassandra-idx of the metrictank config file.
• version v0.12.0-81-g4ee87166 and later reject metrics with invalid tags on ingest by default, this can be disabled via the input.reject-invalid-tags flag.
  if you're unsure whether you're currently sending invalid tags, it's a good idea to first disable the invalid tag rejection and watch the
  new counter called input.<input name>.metricdata.discarded.invalid_tag, if invalid tags get ingested this counter will increase without
  rejecting them. once you're sure that you don't ingest invalid tags you can enable rejection to enforce the validation.
  more information on #1348
• version v0.12.0-54-g6af26a3d and later have a refactored jaeger configuration + many more options #1341
  the following config options have been renamed:
  • tracing-enabled -> jaeger.enabled
  • tracing-addr -> jaeger.agent-addr
  • tracing-add-tags -> jaeger.add-tags (now also key=value instead of key:value)
• as of v0.12.0-43-g47bd3cb7 mt-whisper-importer-writer defaults to the new importer path, "/metrics/import" instead of "/chunks" and
  uses a "http-endpoint" flag instead of "listen-address" and "listen-port".

importer

• bigtable importer #1291
• Make the importer utilities rely on TSDB-GW for authentication and org-association #1335
• fix TTL bug: calculate TTL relative to now when inserting into cassandra. #1448

other

• meta tags (beta feature):
  • Implement series lookup and filtering by meta tag #1423
  • Meta tag enrichment #1433
  • Auto complete with meta tags #1438
  • Batch update meta records #1442
    Left to do: rule persistence.
• fix kafka backlog processing to not get stuck/timeout if no messages #1315, #1328, #1350, #1352, #1360
• memleak fix: Prevent blocked go routines to hang forever #1333, #1337
• update jaeger client v2.15.0 -> v2.16.0, jaeger-lib v1.2.1 -> v2.0.0 #1339
• Update Shopify/sarama from v1.19.0 to v1.23.0
• add orgid as jaeger tag, to ease searching by orgid #1366
• Fix active series stats decrement #1336
• render response metadata: stats #1334
• fix prometheus input plugin resetting its config at startup #1346
• make index/archive tables configurable #1348
• add writeQueue buffer to memoryIdx #1365
• remove tilde from name values when indexing tags #1371
• Jaeger cleanup: much fewer spans, but with more stats - and more stats for meta section #1380, #1410
• increase connection pool usage #1412
• New flag 'ingest-from' #1382
• flush aggregates more eagerly when we can #1425
• Peer query speculative fixes and improvements #1430
• support sharding by tags #1427, #1436, #1444
• Fix uneven length panics #1452

new query api functions

• fallbackSeries #1326
• group #1324
• integral #1325