Adding reset function based on issue

[thebitguru]

Re: #380 Here is a pull request to add a function that resets the cache so multiple result sets can allow StructScan. This is based on @g-rad's approach.

[coveralls]

Pull Request Test Coverage Report for Build 24

• 0 of 3 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.1%) to 71.676%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sqlx.go	0	3	0.0%
<!--	Total:	0	3

Totals
Change from base Build 17:	-0.1%
Covered Lines:	1078
Relevant Lines:	1504

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💛 - Coveralls

[glebteterin]

Ping @jmoiron

[ShoshinNikita]

ping @jmoiron

[dlsniper]

Hello, @ardan-bkennedy, and I recently stepped in to help maintain this project. We are sorting the opened issues and pull requests and from what I can see, this might be better served by other opened PRs. When we'll start merging them, this should be sorted out by automatically resetting the cache thanks to those. Thank you for your contribution.