Add enter, exit function

[Chaho12]

Description

• Support With statement for cursor class #517
• Adds enter, exit function to support With statement, for automatic connection closure
• Did not add any test code, but rather changed a test code to use with statement

Non-technical explanation

Release notes

(x) This is not user-visible or docs only and no release notes are required.
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( ) Release notes are required, with the following suggested text:

* Fix some things. ({issue}`issuenumber`)

[hashhar]

LGTM.

However please be aware that as of today we don't follow DB-API correctly because cursor.close doesn't rollback an in-progress transaction and doesn't prevent re-using the cursor. See #529 for details.

[hashhar]

Also please improve commit message, maybe Add support for using Cursor as a context manager?

[Chaho12]

Thx for sharing history :)