Enable multi-line mode in mycli

You can enable multi-line mode by pressing <F3> key or set it permanently via the config file:

# Multi-line mode allows breaking up the sql statements into multiple lines. If
# this is set to True, then the end of the statements must have a semi-colon.
# If this is set to False then sql statements can't be split into multiple
# lines. End of line (return) is considered as the end of the statement.
multi_line = False