Change config defaults in 0.13

[Felixoid]

• Use max-data-points = 1048576, as it is in ClickHouse 20.8 ClickHouse/ClickHouse@d7871f3
• Use cancel_http_readonly_queries_on_client_close=1, #70
• Use internal-aggregation = true
• Use index table instead of tree
• Don't use [tags] by default
• BREAKING: use integer representation of os.FileMode (0o755)