TODO

• support for distinct
• command line interface
• better table print
• support for order by, offset, limit (allow column name in order by, validate)
• add count min and max functions, eg aggregate functions
• support for uniqueue indexes
• support for btree indexes
• support for parenthesis
• functions rtrim, ltrim, rpad, lpad
• support for *
• add pipe | token
• maybe to create iterator on table
• add exceptions and rename it to UsqlException
• class members should have prefix m_
• add const wherever should be