Rework content on connecting

[msainio]

Proposed changes

Create subsection for connecting to CSC supercomputers under the Computing section. Subsection consists of an overview page as well as separate pages for SSH on Unix-based systems, SSH on Windows, and setting up SSH keys.

• Connecting SectionPage

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[rkronberg]

Should we mention how to connect directly to a certain login node? And list the alternatives. This would also be a good place to mention login node usage policy.

[msainio]

Should we mention how to connect directly to a certain login node? And list the alternatives. This would also be a good place to mention login node usage policy.

Sure!

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