Aws-gate

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* Add new AWS regions

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* Fix regression introduced in 572, which resulted in not being to find bootstrapped plugin
* Plugin version comparison is using more robust mechanism to determine newer plugin version

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* Add bash completion for **exec**(contribution by [kit494way](https://github.com/kit494way))
* Fix ls to show instances without Name tag (contribution by [kit494way](https://github.com/kit494way))
* Pass environment on to subprocess and support running behind a proxy (contribution by [DanSipola](https://github.com/DanSipola))

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* Add **exec** command to be able to execute interactive commands over SSM. Idea by [nc-furstenauw](https://github.com/nc-furstenauw)

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* Default profile and region are now used if hosts profile and region are not defined. This allows to have much leaner config files, especially in situations when multiple hosts are sharing the same profile and region. Contributed by [svalentino](https://github.com/svalentino)
* AWS sessions will look for cached credentials in ~/.aws/cli/cache. Contributed by [becrsh](https://github.com/becrsh)
* Fix Python 3.6 compatibility issue in `subprocess.run`. Tested by [larryon](https://github.com/larryon)

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* Improve instance listing performance in cases when there are many instances connecged to AWS Systems Manager