Separate servers, operations, and backups from sql.core.

[jaredmoo]

No change to contents, just simple move. This separation is needed because servers and operations will soon have a new api-version, so composite swagger will need to to pull databases/pools/etc from 2014-04-04 sql.core.json and servers/operations from 2015-05-01-preview swagger files.

This checklist is used to make sure that common issues in a pull request are addressed. This will expedite the process of getting your pull request merged and avoid extra work on your part to fix issues discovered during the review process.

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[jaredmoo]

Can we keep this change as a pure source code refactor and track any validation fixes in #1107 ? This way the functional and non-functional changes are separated.

[sarangan12]

Agreeing with @jaredmoo comments. The errors are being handled seperately. This is considered simple as a move and thus being approved.

[AutorestCI]

No modification for NodeJS

[AutorestCI]

Azure/azure-sdk-for-python#1084

[AutorestCI]

Azure/azure-sdk-for-ruby#753

[jaredmoo]

Thanks for the very speedy review and merge @sarangan12 !