enh: add wal option to show database command

refactor: add new auth code

doc: SQL reference guide, grant and select

refactor(sync): pre-commit integration

doc: SQL reference guide

update test case about csum

test: add test case

fix: make tdbDebugFlag work

test: update case bug fix

refactor: optimize the memory consumption in tsdbread

fix: handle both null tag values

enh: add wal options to db

fix: set null when all inputs are null for leastsquare function

test: valgrind case

enh(query): add selectivity for output n-1 indifinite_rows function(diff & derivative)

refactor(sync): add pre-commit interface

doc: table, stable, database in sql manual