Merge pull request #731 from zhyass/feature_set

*: fix the bug that the condition after show variables does not take effect #730

Merge pull request #728 from zhyass/feature_set

docs: update how_to_import_and_export_data.md

Merge pull request #727 from zhyass/feature_set

docs: update sql_statements

Merge pull request #726 from zhyass/feature_set

*: change LowerCaseTableNames type to int and add some test cases #725

*: add config lower-case-table-names to support case insensitive table name #725

Merge pull request #714 from hustjieke/feature_complete_delete_statement_#713

*.: fix some comments error and code format #713

*.: fix bug on column field in where | order by clause #713

.*: complete test to improve test coverage #713

*.: complete delete syntax #713

Merge pull request #723 from hustjieke/feature_support_check_table_stmt