Implement INSERT and UPDATE parsing

[gpittarelli]

Implements parsing for INSERT and UPDATE queries, per the MySQL 5.7 grammar. Includes pretty printing + test cases.

(Note: for my own purposes, I've published this branch under @gpittarelli/js-sql-parser)

[albin3]

Great, i'm a little busy these days, i will review it later.

[albin3]

hi, @gpittarelli .

I reviewed the insert part in this pr and there are something need to change / some questions need to confirm:

1. following https://dev.mysql.com/doc/refman/5.7/en/insert.html , simple_table_factor grammar may be should be replaced by identifier.
2. more test cases are needed for for the new code.
3. suggestion: format the code more similar with document in https://dev.mysql.com/doc/refman/5.7/en/insert.html , such as there are three insert grammars in document, we also write it into three lines. So, it's more readable.