Autocompletion bugs & improvements

[hatarist]

(in no particular order)

• datatype completion is broken for the second column (and later)

• only one completion is displayed in case of SELECT * FROM sys<tab>

• table autocompletion should have the current database in mind

• aliased column in subqueries don't work

• autocompletion prepends the table name if called inside the function's parentheses

[hatarist]

Autocompletion should get the list of supported functions/datatypes/whatnot from the server

The lists are currently hard-coded in the clickhouse_cli/clickhouse/definitions.py:

• FUNCTIONS, CASE_INSENSITIVE_FUNCTIONS, AGGREGATION_FUNCTIONS -> SELECT * FROM system.functions; (should also take care of is_aggregate and case_insensitive) for is_aggregate ones, should add suffixes from SELECT * FROM system.aggregate_function_combinators;

• DATATYPES -> SELECT * FROM system.data_type_families;