Async support for the queries in the SQL Lab. WIP.

[bkyryliuk]

Added async support:

• Refactored the tasks.py to return the query id and added ability to run the code async.
• Changed the celery_tests to be more end to end (calling run_sql endpoint instead of celery function)
• Added implementation of async run of the hive and presto queries
• Added dependencies required by pyhive
• Implemented progress bar for the async queries
• Added extra fields to the Query object to improve traceability: limit_used, select_as_cta_used, executed_sql, select_sql

Tackles backend of the: #858, #746, #886

Implement progress bar for the presto / hive queries

Implement remote query execution

It is a preliminary PR and some more things needed to be done.
TODO:

• Unit test async queries (presto and hive engines)
• Add query_status / progress endpoint
• Implement cancel_query endpoint
• Add query_results endpoint
• Find and implement a storage for the query results preview
• Add ttl to the queries / tmp tables (optional)

[coveralls]

Coverage decreased (-2.1%) to 78.432% when pulling e1e3382 on bogdan/query_status_polling into 5688246 on carapal.