Multiline inserts, fix memory leak caused by query_id, fix stack trace when no live server

[splichy]

• feature: support for multiline inserts (some CH drivers are sending FORMAT TabSeparated with multiple rows e.g. Java ExecuteBatch) so we have count number of rows in data
• improvement: log in µs & log only insert statements - SELECTs are not that interesting and actual query isn't logged at all
• improvement: enable debug with ENV var
• fix: memory leak caused by query_id in query params - basicaly every query is unique -> new map[]Table for every query with query_id -> tables were never deleted. I have added two options: clean_interval - all tables which are not updated for clean_interval will be deleted; remove_query_id - will remove query_id=... from query params before create / insert to Table (in our load the mem usage was 800MB+ within ~3h, with remove_query_id is the mem usage stable ~45MB) this can probably solve High Memory Usage #23
• fix: return 503 instead of stack trace when there is no live clickhouse endpoint

[nikepan]

Thank you for this big update!
can you fix travis fail? https://travis-ci.org/github/nikepan/clickhouse-bulk/jobs/717600328