Replaced the --max_returned_rows and --sql_time_limit_ms options to
"datasette serve" with a new --limit option, which supports a larger
list of limits.
Example usage:
datasette serve --limit max_returned_rows:1000 \
--limit sql_time_limit_ms:2500 \
--limit default_facet_size:50 \
--limit facet_time_limit_ms:1000 \
--limit facet_suggest_time_limit_ms:500
New docs: https://datasette.readthedocs.io/en/latest/limits.htmlCloses#270Closes#264
