Support create or replace view/table

[Dandandan]

Adds support for create or replace (external) table

#228

Examples:
https://cloud.google.com/bigquery/docs/reference/standard-sql/data-definition-language
https://docs.snowflake.com/en/sql-reference/sql/create-external-table.html

[coveralls]

Pull Request Test Coverage Report for Build 184656483

• 98 of 103 (95.15%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 91.69%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser.rs	11	16	68.75%

Totals
Change from base Build 175941714:	0.06%
Covered Lines:	4259
Relevant Lines:	4645

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💛 - Coveralls

[nickolay]

I've already "approved" this in GitHub UI earlier, but to confirm: this looks great to me!

[Dandandan]

Awesome @nickolay ! Thanks for the review